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► Increasingly, vehicle technicians must have an understanding of the electrical principles involved in vehicle system operation.
► Atoms contain negatively charged electrons moving around a nucleus, in which there are positively charged protons and neutrons with no charge.
► Atoms with excess electrons have a negative charge and create a negative ion; those deficient in electrons have a positive charge and create a positive ion.
► Free electrons can move from one atom to another if an electrical potential is applied.
► Materials with many free electrons are good electrical conductors.
► Copper is the most common conductor.
► Insulators are materials that do not conduct current easily; an example is plastic.
► Semiconductor refers to a material that conducts electricity more easily than an insulator, but not as well as a conductor.
► Free electrons require a pathway or circuit, and a force to act upon them, such as a battery.
► Like charges repel, and unlike charges attract.
► The attraction of free electrons that creates a force is called voltage.
► The four factors that determine electrical resistance level are the type of material and the length, size, and temperature of the conductor.
► Electrical resistance refers to the degree to which a material opposes the passage of an electrical current.
► Resistance is measured in ohms and is constant in an object unless the temperature changes.
► A semiconductor’s ability to conduct electricity depends on negative electrons and holes.
► The number of charge carriers in a semiconductor can be changed by adding small quantities of impurities (doping).
► The PN junction of a semiconductor is located at the depletion layer.
► Semiconductors can prevent or allow current flow, depending on connection to a current source.
► Semiconductor materials include silicon, germanium, gallium-arsenide, and silicon carbide.
► Electrical circuits contain a power supply, a current flow on/off switch, a functional component, a conductive pathway, and a protection device (e.g., a fuse).
► Voltage is the electrical pressure difference between two points in an electrical circuit.
► The ampere (amp) is the unit used to describe how much current is flowing at a given point within a circuit when the functional component is operational.
► The ohm is the unit used to describe electrical resistance in a circuit or component.
► Direct current (DC) flows in one direction only; alternating current (AC) continuously changes its direction of flow.
► Electrical components can work only on AC or DC, but not both.
► Circuits may be described in terms of continuity, open, short, and high resistance.
► Electrostatic energy occurs when two insulators are rubbed together, with one losing electrons to become positively charged and the other gaining electrons to become negatively charged.
► Thermoelectric energy is produced by joining and heating two different metals.
► Electrochemical energy is produced via electrolysis, which is the immersion of two dissimilar metals in a conducting liquid to break down chemicals into ions.
► Photovoltaic energy is produced via solar energy cells.
► Piezoelectric energy is produced when certain crystals are subjected to mechanical stress.
► Electromagnetic induction is created when a conductor cuts across a magnetic field.
► The effects of electricity include light (LED bulbs), heat (headlights), chemical reactions (lead-acid battery), and magnetism (electric motors).
► Electromagnets are used in relays, solenoids, and motors, while electromagnetic induction is used in ignition coils and transformers.
► Relays are used to control circuits that carry high current flow; they can be normally open (NO) or normally closed (NC).
► Solenoids operate similarly to a relay, but create lateral movement rather than closing a circuit.
► Electric motors rely on magnetic fields to create rotary movement.
► Ohm’s law states that the total resistance of a circuit always equals the voltage divided by the amperage.
► The term “work” refers to transforming one form of energy into another.
► Power refers to the rate at which work is done, or the rate of transforming energy.
► The watt is the unit of power.
► Kirchhoff’s current law states that electrical current entering any junction is equal to the sum of the current flowing out of the junction.
► In a series circuit, current can flow in only one path and all electrons flow at the same rate.
► Voltage drop refers to the pressure lost by driving the current through a resistor.
► The electrical properties of a series circuit are as follows: current flow is the same in all parts of the circuit; the applied voltage is equal to the sum of the individual voltage drops; and total circuit resistance is equal to the sum of the individual resistances.
► All components in a parallel circuit are directly connected to the voltage supply; hence the voltage across each component is equal to battery voltage.
► Parallel circuit laws are as follows: the voltage across all branches of a parallel circuit are the same; the total current equals the sum of the current flowing in each branch; the amount of current in each branch is inversely proportional to the resistance of the branch; and the total resistance of a parallel circuit can be calculated as RT = (R1 × R2) divided by (R1 + R2).Or, RT = 1/ 1/R1 + 1/R2 + 1/R3.
► Series-parallel circuits contain both a series circuit and a parallel circuit.
► Electrical components must be correctly connected onto circuits and may have numbered or marked terminals to ensure proper connection.
► Circuit protection devices, which break the circuit during excessive current flow, are fuses, fusible links, and circuit breakers.
► Resistors are used to control voltage that reaches various components because they resist the current running through them.
► Resistor types include fixed, variable, thermistors, metal oxide varistors, and ballast resistors.
► Resistors are rated by both resistance value and power rating.
► Resistance value is indicated by colored bands, and tolerance is indicated by the number of identifying bands.
► Variable resistor types are rheostats, potentiometers, and thermistors.
► Thermistors are a type of conductor in which resistance value is affected by temperature.
► Capacitors are used to store electrical energy and are rated by capacitance, which is the amount of change stored in each plate for a given potential voltage between the plates.
► Diodes are used to restrict current flow to one direction only.
► Transistors (NPN and PNP types) are used as switches and to amplify currents.
► Control modules are designed to monitor multiple inputs from sensors and circuits and respond to those inputs.
► Delay circuits can turn on or off an electrical device after a specified time delay.
► Microprocessors are designed to monitor and control most electrical systems on a modern vehicle.
► Most vehicle wires are braided copper with plastic insulation, but other types are shielded wires and ribbon.
► Wire shielding to prevent noise (unwanted electromagnetic induction) can be twisted pair, Mylar tape, or drain lines.
► Proper operation of electrical circuits requires correct wire size.
► Length and diameter of a cable determine its resistance.
► Copper has low resistance value, although as the wire length increases, so does resistance within the wire; therefore, the cross-sectional area needs to increase to overcome resistance.
► Terminals and connectors are fitted to the ends of cables to provide low-resistance cable termination.
► Terminals can be push-on spade terminals, eye ring terminals, and solder-type terminals.
► Connectors can be permanent cable joiners, wiring harness connectors, or male or female connectors.
► Wiring harnesses are used to bind wires together within a sheath of insulating tape or tubing.
► Wiring diagrams are generally split up into systems and subsystems.
► Microprocessors and their assorted components are mounted on circuit boards with conductive tracks designed to connect electronic component leads with one another.
► Electronically controlled systems are integrated to a multiplexed serial communications network, such as a controlled area network bus (CAN-bus).
► Fiber-optic cables can transmit light signals over very long distances.
► Electrical measurement tools include the ammeter, voltmeter, ohmmeter, and digital multimeter.
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► An alternative fuel is any fuel that powers a vehicle that is not petroleum-based motor oil.
► Alternative fuels are not new; they have been around since the 1890s.
► Alternative fuels have to meet the California Air Resources Board (CARB) standards to be certified.
► The push for alternative fuels is driven by the need for enhanced security, environmental concern, and economic factors.
► Alternative fuel is regulated by many different acts, starting in 1992.
► The Environmental Protection Agency (EPA) is the driving force behind alternative energy.
► There are many different standards for low-emission vehicles, beginning in the early 1980s and growing progressively stringent into 2012.
► Alternative vehicles are designed to reduce emissions and be more economical to operate.
► Compressed natural gas (CNG) and liquefied natural gas (LNG) were first introduced in the 1980s, but due to lack of refilling stations, they did not sell well to the consumer.
► The process to use either CNG or LNG requires the vehicle engine to be able to run on flexible fuels.
► CNG and LPG must be stored in special cylinders that will withstand pressures and damage.
► CNG and LPG containers are fitted with special pressure relief systems to release pressure as required.
► CNG and LNG must be protected from a heat source. In some designs, special heat shields are installed around the exhaust system to protect the container from excess heat.
► Leaks can be identified by using a special explosion meter that will find methane gas leaks.
► Biofuels are made by chemically combining natural oils from soybeans, cottonseeds, canola, animal fats, algae, jatropha seeds, or even recycled cooking oil with an alcohol such as methanol or ethanol, and a catalyst such as lye.
► There are different qualities of biodiesel fuels, and they should not be confused with the fuel made from old vegetable oil.
► The one main disadvantage to biodiesel is that starting in cold weather may require longer cranking of the engine.
► The military is the driving force in the use of alternative fuels like biodiesel.
► Biodiesel produces less emission than similar diesel fuels.
► Biodiesel has higher water content than traditional diesel fuels.
► Just like with typical diesel fuel, the centane number of biodiesel must be correct for overall engine performance, typically around 46–57; the higher the better.
► Ethanol is being used mainly to lower fuel emissions in vehicles and is made from three products: sugars, grains, and algae.
► Methanol or wood alcohol is being used in E85 vehicles, which means 85% of the fuel mixture is methanol.
► The advantage to methanol is the lower output of emissions.
► The main disadvantage with methanol is that it cannot be burned in conventional vehicles without major engine modifications.
► Biobutenol is similar to ethanol, but butenol has characteristics similar enough to gasoline that it can be transported through the existing petroleum (pipeline) distribution infrastructure.
► Biobutenol shows promise but is in the early stages of development.
► Fuel cell technology has been used a number of years by NASA; given the current need for alternative fuels, it has pushed for another look at this technology by several manufacturers.
► Fuel cells are complex systems that require oxygen and hydrogen to produce water to operate a vehicle.
► Fuel cells have zero pollutants; they exhaust only water.
► There are four elements to a fuel cell: the anode, cathode, electrolyte, and catalyst.
► Fuel cells do not produce enough energy by themselves; to achieve the required power they must be stacked.
► The electric motor shows great promise because it has fewer moving parts, less maintenance requirements, good low-speed torque output, and increased reliability.
► The computer gives the electric motor new life and has some advantages; the biggest disadvantage is the electric motor must have a battery to run it.
► Hydrogen fuel cells are simple and have three times the energy of gasoline. Fuel cell vehicles, however, are more efficient and cleaner.
► Battery electric vehicles (BEVs) are making a comeback with the addition of computer technology and lithium batteries.
► The Chevy Volt was supposed to be the first BEV, but it is really a hybrid, since it has a gasoline engine to recharge the battery.
► Hybrids have been used since World War II.
► The locomotives on the railroad tracks today are diesel electric; the engine charges the batteries and the locomotive runs on the batteries.
► Many city buses are diesel electric, which demonstrates that hybrid technology is not new; it is being redefined, with the new vehicles using computers to control operations.
► The engine in hybrids can be much smaller, as its main purpose is to recharge the hybrid’s battery. The hybrid gets most of its power from the battery running the electrical drives.
► When you think of hybrids, think of electrical circuitry. There are series, parallel, and series parallel designs.
► On series hybrids, the engine runs only to supply the electric motor or charge the batteries.
► On parallel hybrids, the engine runs to charge the battery and directly assist propelling the vehicle.
► On series-parallel hybrids, the engine runs to charge the battery, operate the electric motor, and assist with propelling the vehicle all at the same time.
► Hybrids offset the power lost by internal combustion engines (ICEs) in several ways. One of the most efficient is the regenerative braking system.
► There are numerous hybrids, from plug-in to extended-range. They all work basically the same way: They allow the vehicle to be propelled by the electrical power. Thus, they are more fuel efficient.
► The hybrid normally starts out on electrical power, and as the need changes, the engine will come on to assist or recharge the batteries, depending on the design.
► The ICE is turned off during deceleration and braking.
► The ICE needs to start and run at higher rpm for peak efficiency.
► Hybrids can be dangerous. Always refer to the appropriate repair information.
► In hybrids, it is usually the orange wires that indicate high voltage. Other colors may be used, so check the manufacturer’s information. Always wear special gloves to remove the access plugs to disable hybrids.
► Anytime service is performed, the technician needs to ensure that the hybrid is not in the ready mode and that everything is off.
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► Most cooling systems rely on coolant, a special mix of chemicals (anti-freeze) and water.
► Coolant absorbs heat from the engine, is cooled in the radiator, and flows back to the engine to absorb more heat.
► Heat travels in one of three ways: conduction, convection, or radiation.
► Coolant works to keep an engine from overheating and from freezing.
► Coolant must contain anti-freeze to prevent the water content from freezing and to reduce corrosion.
► Anti-freeze contains either ethylene glycol (toxic) or propylene glycol (nontoxic).
► The combination of water and anti-freeze lowers the freezing point and raises the boiling point of both components.
► Manufacturers can create more efficient combustion by raising the engine’s operating temperature, creating more pressure, and causing coolant to boil at a higher temperature.
► Radiator caps maintain a specified pressure throughout the cooling system, generally 13–17 psi (89.6–117.2 kPa).
► Changing coolant regularly prevents acid buildup and electrolysis.
► The stationary parts of the cooling system (heater core and radiator) are connected to the engine via radiator and cooling hoses.
► Modern vehicles have replaced the thermo-siphon process for moving coolant through the engine with a water pump that forces coolant through the system.
► An engine thermostat regulates coolant circulation, keeping it in the engine until the engine reaches operating temperature.
► Engineers have developed a reverse-flow cooling system in which coolant is first pushed through the cylinder head, thereby better equalizing temperature between the block and head, which extends the life of the head gasket.
► Engines with the reverse-flow cooling system must have a surge tank to capture steam and reconvert it to coolant.
► Rotary engines use similar cooling systems to piston engines, with a radiator, thermostat, radiator hoses, and water jackets.
► The radiator’s function is to allow coolant to pass through it and to conduct heat away from the engine.
► Cooling tubes in the radiator core run in a vertical (down-flow) or horizontal (cross-flow) design.
► Radiator pressure caps contain a spring-loaded valve to allow excess coolant to pass into the overflow container, and a vacuum valve to allow coolant to be pulled from the overflow container back into the radiator when it is needed.
► A surge tank is situated as the highest component so that it collects any air present in the system and allows for easy air removal.
► In a recovery system, coolant flows into an overflow container and then back into the radiator so that no coolant is lost.
► The thermostat’s valve is controlled by a wax pellet that melts and expands and forces the valve open against spring pressure.
► Thermostats installed on the inlet side of the engine better control the amount of cold water flowing into the engine.
► The water pump uses centrifugal force to drive coolant into the water jackets.
► A fan clutch is driven by an accessory belt and uses a viscous fluid to control speed changes of the fan, determined by air temperature from the radiator.
► A solenoid-controlled fan clutch replaces the bimetallic spring with an electric solenoid controlled by the power train control module.
► Radiator hoses must be correctly clamped to the radiator assembly or a leak will develop.
► Some heater hoses contain a coolant control valve to regulate coolant flow when the air conditioner is turned on.
► The three types of drive belts for the water pump are V-belts, serpentine belts, and toothed belts.
► To ensure minimal slippage, drive belts are tightened around the pulley by tensioners.
► Either a temperature gauge or a temperature light can function as a coolant temperature indicator.
► Coolant passages are critical to the transfer of heat energy so coolant must be serviced regularly to prevent the passages from becoming clogged.
► The heater box contains air doors and actuators that work to control passenger compartment airflow.
► IAT coolant is the standard green coolant used in many vehicles and must be changed every 2 years or 24,000 miles (39,000 km).
► OAT coolant is an extended-life coolant that should be changed every 5 years or 150,000 miles (241,000 km).
► HOAT coolant (yellow) combines inorganic and organic additives and is also an extended-life coolant.
► POAT coolant, the newest type, is a very long-life coolant that should be changed every 7 years or 250,000 miles (402,000 km).
► Cooling systems need regular maintenance to ensure engine longevity.
► Common cooling system diagnostic concerns include coolant leaks, thermostat that is stuck closed or open, faulty water pump, inoperative cooling fan, or failed head gasket.
► Test pH concentration of the coolant to ensure the anti-freeze acid inhibitors are working correctly.
► Measure the voltage of the coolant to determine if electrolysis is occurring due to acidic coolant or faulty grounds.
► Always follow EPA regulations for handling and disposing of coolant.
► Coolant condition and level should be checked regularly; coolant should be at the correct level mark (upper or lower) according to engine temperature.
► When removing and replacing a radiator, be sure to properly catch, handle, and dispose of or replace the coolant.
► Do not attempt to remove or replace the thermostat until the engine has cooled for at least 30 minutes.
► Potential engine drive belt problems can be belts that are cracked, oil soaked, glazed, torn, or bottomed out.
► Coolant freeze point can be verified by a hydrometer or refractometer, both of which indicate the specific gravity of the fluid, revealing the ratio of anti-freeze to water.
► Removing and reinstalling the heater core can be challenging; taking pictures as you go is highly recommended for ease of reassembly.
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► Most modern vehicles use internal combustion engines.
► Internal combustion engines are typically either piston (spark ignition, using reciprocating motion of pistons) or rotary (spark ignition, using planetary motion).
► Piston engines can be spark ignition (passenger vehicles; uses a spark plug) or compression ignition (diesel vehicles; no spark plug).
► Pressure and temperature have a direct relationship in that when pressure rises so does temperature, and vice versa.
► Internal combustion engines work by heating a gas, which increases pressure (thermal expansion), creating force to push the piston down the cylinder.
► Pressure and volume have an inverse relationship: when one increases, the other decreases.
► Force (effort) tends to cause movement, which creates work; the speed at which this happens is known as power.
► Work = distance moved × force applied.
► Power = distance × force / time in minutes.
► Engine power is measured by the amount of torque (turning effort) applied to the crankshaft, times the RPM at which it is turning divided by 5252.
► Torque and power produced by an engine are called engine output.
► Horsepower refers to the speed at which torque is produced.
► Load factor refers to the period of time a vehicle can operate at maximum speed and power.
► Piston stroke refers to the distance traveled from top dead center (TDC) to bottom dead center (BDC) (or BDC to TDC).
► Internal combustion engines have either a two-stroke or four-stroke cycle.
► In a four-stroke cycle, five events must occur: intake, compression, ignition, power, and exhaust.
► The compression ratio of an engine is based on cylinder volume at BDC compared to cylinder volume at TDC, and can be affected by changes in piston stroke, piston head shape, head gasket thickness, and combustion chamber size.
► Piston displacement (the volume of movement from BDC to TCD) is calculated as: bore squared × 3.14 × stroke / 4.
► Engine displacement is calculated as piston displacement × number of engine cylinders.
► Two variations on the typical four-stroke spark ignition engine are the Miller cycle engine and the Atkinson cycle engine, both of which use valve timing variations to create unequal compression and expansion strokes.
► The Miller cycle engine has an engine-driven compressor that functions at high load and speed to boost power output.
► The Atkinson cycle engine is ideal for hybrid vehicles, as it has a lower power output and torque than conventional engines.
► Valve overlap refers to the short time that both intake and exhaust valves are open, allowing more air and fuel into the engine during high power high rpm.
► Major components of an internal combustion engine include: cylinder block, crankshaft, flywheel, connecting rod and piston, intake manifold, oil pan, oil pump, exhaust manifold, cylinder head, valve train, and engine camshaft.
► The cylinder block, the largest engine component, includes cylinder bores, coolant and lubrication passages, and the crankcase.
► The function of the crankshaft is to convert the piston’s reciprocating motion into rotary (turning) motion.
► The flywheel stores energy from each piston’s power stroke to smooth out the power strokes.
► The connecting rod connects the piston to the crankshaft and causes piston movement (via the crankshaft) during non-power strokes.
► Components that make up and support the piston are: piston head, piston rings (compression and oil control), ring grooves, ring lands, piston skirt, pin hole, and pin boss.
► Compression and combustion gases can leak past piston rings and enter the crankcase; this is known as blowby.
► The purpose of an intake manifold is to deliver air or air and fuel to the cylinder head.
► Oil for the engine lubrication system is stored in the oil pan.
► The camshaft opens the valves and allows them to close at the right time, which ensures correct engine operation.
► Parts of the camshaft lobe include: base circle, nose, cam lobe centerline, and cam lobe ramps.
► Engineers designing camshaft lobes must consider the issues of lift and duration, as well as the cam centerline and separation.
► Parts of an intake valve include: head, face, margin, and stem.
► The intake valve is typically larger and tends to run cooler than the exhaust valve.
► Exhaust valves are typically smaller, allow exhaust to exit the cylinder, and tends to be run hotter than intake valves.
► Modern automotive engines have valves arranged in the cylinder head above the piston, known as an I head arrangement.
► The valve lifter can be hydraulic or mechanical and transfers motion from the cam lobe to the valve train or directly to the valve.
► Roller rocker arms act as levers to increase the camshaft’s lift of the valve.
► Valve clearance must be accurate, so as not to create noise (meaning clearance is too high) or a loss of compression past the valve (clearance is too low).
► Timing of when valves open and close is vital to proper engine function; timing belts will need periodic replacement and must be aligned with engine timing marks.
► Valve timing can be modified during engine design by advancing or retarding cam timing, which gives the effect of more torque and power at a lower rpm or higher rpm range, respectively.
► Variable valve timing allows cam timing to be adjusted during engine operation.
► Cam actuators can be a twisted gear arrangement or a vane-type phaser.
► The engine control module (ECM) controls variable cam timing using the following inputs: mass airflow sensor or manifold absolute pressure sensor, throttle position sensor, intake air temperature sensor, engine coolant temperature sensor, and crankshaft position sensor.
► Using a pulse width modulation signal, the cam solenoid regulates amount and direction of oil flow to the cam phaser.
► Engine design—freewheeling or interference—determines the amount of damage that will result if the timing belt breaks.
► Two-stroke engines use the piston to open and close intake and exhaust ports allowing air-fuel to enter the cylinder.
► All events of an internal combustion engine are accomplished by a two-stroke engine within one up and one down stroke of the piston.
► Two-stroke engines use either a reed valve or rotary valve to allow air and fuel into the crankcase.
► Two-stroke engines eliminate the camshaft and valve train, making them lighter than four-stroke engines.
► Four-stroke engines release fewer hydrocarbons into the atmosphere and are more likely to meet EPA regulations.
► Rotary, or Wankel, engines use a rotor in place of a piston and move it in an epitrochoid curve to create a nearly vibration-free engine operation.
► Rotary engines have two spark plugs—leading and trailing—per rotor to enable complete combustion.
► The rotor moves along the curved surface of its housing and pushes on an eccentric shaft to produce power.
► A rotary engine cycle has four phases: intake, compression, power, and exhaust.
► Each of the three faces of the rotor act as a combustion chamber, and have a power pulse every revolution of the rotor.
► The Renesis rotary engine is designed with improved fuel economy via modified intake and exhaust ports.
► A Renesis engine can be low output (for automatic transmissions) or high output (for manual transmissions).
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► Ignition systems have a primary (low-voltage) circuit to connect and disconnect the ignition coil and a secondary (high-voltage) circuit to send voltage from the battery to the spark plug.
► Common components of an ignition system are the spark plugs, high tension leads ignition coil, and ignition-coil triggering device.
► Principles of an ignition system involve a circuit activating the ignition coil, which converts the battery’s low voltage to high voltage. The voltage then travels to the spark plug in each cylinder, igniting the air–fuel mixture and creating enough pressure to push down the pistons.
► The original contact breaker ignition system was replaced with an electronic ignition system of the distributor type.
► Modern systems are direct ignition systems (or coil-on-plug), which have a dedicated coil for each cylinder.
► The amount of available voltage should always be higher than the amount of required voltage.
► As ignition components age and become worn, required voltage increases and available voltage decreases.
► Spark timing is affected by any of these factors: air–fuel ratio, detected knock, engine speed, engine load, engine temperature, and throttle position.
► Spark timing must be correct in order to give the air–fuel mixture enough time to burn.
► Modern vehicles have electronically programmed spark timing via the PCM; older vehicles mechanically advance or retard the spark timing.
► Common points on an ignition switch are the lock and off functions and the accessory, on/run, and start/crank positions.
► Automatic transmission vehicles may employ a transmission shift interlock device to ensure that the gear selector is in park before key removal can occur.
► Standard ignition coils contain primary and secondary windings around a rod-shaped laminated iron core.
► The main difference among types of ignition systems is the method used to control the primary circuit to produce the secondary spark.
► In the primary circuit, a magnetic field develops that is interrupted by the ignition triggering device, thus collapsing the field and returning stored energy to ignition coil terminals.
► Because the secondary winding has approximately 100 times as many turns as the primary winding, it can produce 100 times greater voltage.
► Basic contact breaker point ignition systems are comprised of the battery, ignition switch, ignition coil, contact breaker points, capacitor, distributor, and appropriate voltage-connecting wires and leads.
► The purpose of the distributor is to transfer the spark to the spark plugs with the correct sequence and timing.
► The distributor cap provides rotor and spark plug lead connection.
► The distributor controls ignition timing in relation to speed via a centrifugal advance mechanism and ignition timing in relation to vehicle load via a vacuum advance mechanism.
► Vehicles regulate voltage to the ignition system via a ballast resistor, which is inserted in the primary circuit and lowers the voltage.
► Spark plugs all have at least one, and up to four, side electrodes, as well as an internal resistor to suppress voltage spikes and prevent radio frequency interference.
► Spark plugs are identified by thread size or diameter, reach or length of thread, and heat range or operating temperature.
► Spark plug components include the metal case, insulator, terminal, side electrode, and center electrode.
► To work effectively, spark plugs must have proper reach (distance from sealing area to end of spark plug threads) and proper heat range (operating temperature, generally 746°F to 1,460°F [400°C to 800°C]).
► High-tension leads carry a high-voltage spark from the ignition coil to the distributor cap and on to the spark plugs.
► Engine timing can refer to valve timing or ignition timing.
► How long the contacts are closed and current is flowing in a contact breaker system is determined by the dwell angle.
► Electronic ignition systems electronically trigger the primary circuit (rather than using a contact breaker).
► The triggering device of an electronic ignition system can be a magnetic pulse generator (pickup coil) or a Hall-effect switch.
► Ignition modules process information from various sensors and then interrupt the signal to the primary winding of the ignition coil.
► Induction-type systems use a magnetic pulse generator with a stator and a reluctor attached to the distributor body and shaft, respectively.
► Induction-type systems produce an alternating current voltage.
► The internal module control circuit receives the trigger signal.
► The reluctor teeth spin past the stator, turning on and off the primary winding and causing the secondary windings to generate a high-voltage spark at the end of each cylinder’s compression stroke.
► Hall-effect systems use a potential difference, or voltage, which is used as a switch device.
► In a Hall-effect system, the magnetic field is alternately blocked and exposed by an interrupter ring.
► Some ignition systems use a phototransistor to receive light from an LED and transform it into a voltage output signal.
► In distributorless ignition systems, the distributor is eliminated so crankshaft and camshaft position sensors help determine when to send a signal to the coil’s primary windings by monitoring which cylinder is approaching its power stroke.
► In a six-cylinder, waste spark engine, each set of two cylinders is paired with an ignition coil. The cylinders alternate between an event cylinder and a waste cylinder.
► The PCM controls spark timing for distributorless ignition systems via information from the following sensors: mass airflow sensor, manifold absolute pressure sensor, throttle position sensor, cam and crank angle sensors, engine speed sensor, knock sensor and coolant temperature sensor.
► Special tools and equipment for ignition system diagnostics include the spark plug socket, spark plug gapping tool, high-tension wire puller, spark tester, test light, a digital multimeter, scan tool and an oscilloscope.
► Oscilloscopes test the condition of the secondary circuit and can show if voltage to any of the cylinders is too high, too low, or nonexistent.
► The first step in diagnosing ignition system issues is to conduct a visual inspection to look for loose connections, broken or corroded terminals, or any components that need replacing.
► Inspect the primary and secondary circuit wiring for cuts, abrasions, and signs of arcing.
► Test the ignition coil for primary and secondary winding resistance.
► If the vehicle will not start, performing a spark test is a good step.
► Test to ensure that the spark plug wire, distributor cap and rotor, crankshaft and camshaft position sensors, and ignition modules are in proper working order.
► Always follow manufacturer-recommended procedure for diagnosing each ignition system component.
► Spark plugs and spark plug wires will wear over time and require replacement; check the manufacturer’s recommendations for replacement schedules.
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► Most automotive shops and technicians send their engine machining work to a specialty machining shop where components are restored to factory specifications.
► The measure of surface roughness is based on surface valleys and peaks and is specified as surface roughness area (Ra).
► The deck height of an engine block must be identical at each cylinder in order to maintain equal compression values.
► The engine cylinder block dowel pinholes are used as alignment guides for the cylinder head and cylinder head gasket.
► Damaged cylinders must be rebored to fit oversized pistons.
► Boring bars, which position and align a single-point tool, can be portable, semiautomated, or CNC style.
► After boring, the cylinder walls must be honed to the proper surface texture.
► A ball hone may be used to reapply the cylinder’s crosshatch pattern.
► Most hones are self-tensioning but must be adjusted to the correct speed to achieve the desired angle of crosshatch.
► A torque plate may be used to keep the cylinder true to the machined dimensions when honed.
► Main bearing bores must be properly aligned to prevent premature bearing failure and crankshaft failure.
► The engine block must be line bored or line honed to correct a bore alignment issue.
► Oil clearance can be checked quickly with Plastigauge or by subtracting the size of the main bearing journal from the size of the main bearing bore with bearings installed.
► Crankshaft journals must have clean surfaces, with imperfections polished out.
► Crankshaft rods must all be cut to the same size, as must all main journals.
► A crankshaft can be spray welded to add enough surface material for grinding.
► Crankshaft oil passage holes must be chamfered before journal polishing begins.
► The big end of a connecting rod must be resized to ensure proper rod cap alignment; this can be done with a rod honing machine or a rod boring machine.
► Before disassembling a non-adjustable -valve-type cylinder head, measure and record the valve installation height.
► Cylinder heads should be magnafluxed, using the wet or dry method, to check for cracks.
► Aluminum cylinder heads cannot be magnafluxed; therefore, they must be pressure tested via water or a pressure testing bench.
► Overhead cam engines may have camshafts that lose lubrication if oil pressure drops or misaligned cam bores if the engine overheats.
► Cam bores must always be aligned, typically within 0.004" (0.1 mm) of each other.
► The four methods of repairing valve guides are knurling, reaming the guide oversize and using a valve with an oversized valve stem, installing a thin-walled bronze liner, or installing a thick-walled guide (bronze or cast iron).
► When grinding valve faces, be careful not to grind away too much valve margin.
► Hardened valve seats are installed to prevent the valve from sinking into the head.
► Valve seats may be made of nickel alloy, chrome alloy, cobalt alloy, stainless steel, cast iron, or tungsten steel (for CNG or propane engines).
► Valve seats can be refurbished with stones or cutters.
► Check valve seat contact, valve seat runout, and valve guide-to-valve stem clearance.
► It is critical to measure valve stem height after machining to ensure that the valve will close once the valve train is installed.
► Measure valve spring height and adjust to correct height with shims.
► Cylinder head resurfacing may be performed if the head deck surface is found to be warped or if there is excessive pitting.
► The majority of production engines are “prebalanced” before leaving the factory.
► Engines can be internally or externally balanced.
► Crankshaft assembly parts are divided into rotating (moving in a circular motion) and reciprocating (moving up and down) weight categories.
► Equipment needed to simulate balance of a V8 engine includes an engine balancer, a connecting rod balance fixture, a gram scale, gram calibration weights, bob weights, lead shot, a disc sander, and an equipment lathe or milling machine.
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► The principle behind hydraulic brakes is Pascal’s Law, which states that pressure applied to a fluid in one part of a closed system will be transmitted without loss to all other areas of the system.
► A substantial leak in the hydraulic braking system will prevent enough pressure from building to exert the necessary braking force.
► Engineers design brakes that have precise (but unequal from front to back) amounts of braking force at each wheel.
► The three variables related to pressure and force in hydraulic systems are: input force, working pressure, and output force.
► Main components of the hydraulic braking system are: brake pedal, brake fluid, and master cylinder.
► The brake pedal multiplies force from the driver’s foot to the master cylinder.
► Brake fluid has a high boiling point, a low freezing point, and is hygroscopic (absorbs water).
► Brake fluids are graded by the Department of Transportation on: pH value, viscosity, resistance to oxidation, stability, and boiling point.
► Master cylinders convert force exerted from the brake pedal into hydraulic pressure to activate wheel brake units.
► Types of master cylinders are: single piston and tandem (required on modern cars).
► Single piston master cylinders use a primary cup to seal pressure in the cylinder and a secondary cup to prevent fluid loss.
► A single piston master cylinder traps brake fluid and forces it into the brake lines.
► Residual pressure valves are used on drum brake systems to maintain brake fluid pressure and prevent air entry when the brakes are off.
► Modern vehicles have tandem master cylinders to ensure braking ability in at least one circuit despite a leak.
► Differential pressure switches monitor loss of pressure between the hydraulic circuits.
► Braking units can be split front-to-rear, diagonally, or in an L shape.
► Diagonal and L-shaped braking splits retain 50% braking capability even if half the system fails.
► Quick take-up master cylinders work to compensate for the large running clearance maintained by low-drag brake calipers.
► It can be dangerous to add brake fluid without diagnosing the reason for a low fluid level.
► Always ask customers questions to gather diagnostic information; try a test drive to understand what the customer is experiencing.
► Always try to discern the root cause of a vehicular problem.
► Common tools that are used to repair hydraulic brake systems are: brake bleeder wrenches, vacuum brake bleeders, pressure brake bleeders, and valve gauge sets.
► Bleeding the brakes removes air form the hydraulic braking system.
► The three most common brake bleeding methods are: manual, pressure, and vacuum (gravity is also used).
► Flushing the brake fluid involves bleeding out the air and replacing the old brake fluid with new.
► Always select the proper grade of brake fluid for the vehicle you are working on.
► Determining if brake fluid should be flushed can be done by: time/mileage, DVOM-galvanic reaction test, boiling point test, or test strip.
► DVOM-galvanic reaction test, brake fluid testers, and brake fluid test strips can all be used to check for brake fluid contamination.
► Manual bleeding requires the least amount of tools and is best when a small amount of bleeding is needed.
► Pressure bleeding requires more equipment and is best when the hydraulic system needs a full flush.
► After bleeding, always check that bleeder screws are properly tightened with no leaks, refill master cylinder and reinstall reservoir cup, and properly dispose of brake fluid.
► Brake pedal inspection includes brake pedal height, free play, and travel.
► Free play is the clearance between the brake pedal linkage and master cylinder piston.
► Brake pedal travel is the distance from its rest position to its applied height.
► Check the master cylinder for leaks if: the brake fluid is low in the reservoir, the brake warning light is on, or the brake pedal reserve height is too low.
► Inspect the master cylinder for internal leaks only if the brake pedal sinks.
► Bench bleed the master cylinder prior to installing it to minimize time needed to bleed the hydraulic brake system.
► Master cylinder pushrod length should only be adjusted if: someone changed the adjustment setting, the brake pedal linkage has been repaired or adjusted, or the power booster is being replaced.
► Brake lines are made of double-walled steel and coated to help resist corrosion.
► Damaged brake lines should be replaced not repaired; always use the correct tubing bender to avoid kinks.
► The two types of brake line flares are inverted double and ISO.
► Brake hoses transmit the brake system hydraulic pressures to the wheel units and must be of the proper length to be effective.
► Pinching or kinking a brake hose can cause it to fail.
► Inspect brake hoses for: cracks, bulges, abrasion or wear, kinks, and internal breakdown.
► Hydraulic braking systems use proportioning valves, metering valves, pressure differential valves, or anti-lock hydraulic control units to modify hydraulic pressure.
► Proportioning valves reduce brake pressure to the rear wheels and are pressure-sensitive or load-sensitive.
► Load-sensitive proportioning valves adjust rear brake pressure according to the weight of the vehicle’s load.
► Pressure-sensitive proportioning valves use a poppet piston to limit the rate of braking pressure increase to the rear brakes.
► Metering valves work to ensure rear brake pressure is applied before front brake pressure.
► The combination valve combines individually operating proportioning valves, metering valve and pressure differential valve in one unit and cannot be repaired.
► Brake warning lights alert drivers to: engagement of the parking brake, low brake fluid intake, and unequal pressure in the hydraulic brake system.
► Stop lights are mounted on the rear of a vehicle and alert other drivers that the vehicle is being braked.
► As of 1986, all vehicles must have a center high-mount stop lamp (CHMSL) to reduce incidence of rear-end collisions.
► Power brake units are either vacuum assist (most common) or hydraulic assist.
► Vacuum boosters have single or dual diaphragms to extract power from atmospheric pressure and transmit force to the master cylinder.
► A 12-inch vacuum booster is capable of generating enough psi to stop a vehicle weighing thousands of pounds.
► A vacuum booster works off of the difference -between manifold vacuum and atmospheric pressure; a difference in these pressures creates more force on the master cylinder pistons.
► Inspect and test power brake systems whenever the customer complains that the brakes are dragging, the brake pedal is harder to push than normal, the pedal height has changed, or the engine operation changes more than a minimal amount when the brake pedal is applied.
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► The suspension system is designed to absorb road shock and vibrations.
► Unsprung weight refers to the vehicle parts not supported by springs (wheels, tires, brake and steering assemblies); this weight should be kept as low as possible.
► Metal springs, rubber, and air all work to provide suspension system support by absorbing some amount of force.
► Springs react to road shock by not immediately returning to their original state. They may oscillate—that is, fluctuate in length, until the energy from the road shock is dissipated.
► Vehicle movement may be due to yaw, pitch, or roll.
► Suspension system components include the springs, axles, shock absorbers, arms, rods, sway bars, steering knuckle, bushings, and ball joints.
► Types of springs include coil springs, leaf springs, and torsion bars.
► Coil springs can be cylindrical, barrel shaped, or conical and are used on the front suspension of most modern light vehicles.
► Leaf springs are primarily used on rear-wheel drive vehicles and consist of multiple flat springs made of tempered steel.
► Functions of axles include helping support vehicle weight, maintaining wheel position, providing forward propulsion of the vehicle, and transmitting torque to the wheel.
► Axle types include straight, dead, full-floating, or semi-floating.
► Types of shock absorbers are hydraulic, gas pressurized, and adjustable (which can be load adjustable, annual adjustable rate, electronic adjustable rate, and automatic load adjustable).
► Shock absorbers use the resistance of a rod and piston, and oil and disc valves, to provide a dampening effect on the force created by the bumps and jolts of driving.
► Manually adjustable air springs can be incorporated into rear shock absorbers for vehicles designed to carry heavy loads.
► The dampening rate of electronic adjustable rate shock absorbers can be manually or automatically altered.
► The primary load-bearing elements of a SLA suspension system are known as control arms, which attach to the wheel assembly on one end and the chassis on the other.
► The primary load-bearing elements on a MacPherson strut suspension system is the strut itself.
► Bushings act as bearings at suspension fulcrum points, allowing movement of the component without losing its alignment.
► The two types of auto body construction are unibody (most common) and full frame.
► Types of suspension systems are solid (beam) axles, independent, rear, front, adaptive air, and computer controlled.
► A live axle transfers power from the engine to the wheels; a dead axle does not transmit any drive.
► Independent suspension allows for lower unsprung mass.
► Independent suspension systems adjust wheel camber individually.
► Struts are commonly used in independent suspension systems; the most common type is the MacPherson strut.
► Types of rear suspension systems are rear independent, rear-wheel drive independent, rigid-axle leaf spring, rigid-axle coil spring, and rigid nondrive.
► Rear suspension systems in front-wheel drive vehicles are designed to keep the rear tires in contact with the road, and aligned with front tires.
► The rear suspension system on a rear-wheel drive vehicle must allow for swiveling of the front wheels during steering; on four-wheel steering vehicles, the system must allow for swiveling of rear wheels as well.
► Front suspensions are generally either independent (front wheels move independently) or solid (an axle forces the front wheels to move together).
► Front suspension system types include MacPherson strut, short/long arm (SLA), and torsion bar.
► Adaptive air suspension systems electronically control the height of all four wheels based on vehicle speed and load.
► Types of computer-controlled suspension systems are active, hydraulic actuated, electromagnetic rheological, semi-active, and solenoid/valve actuated.
► Wheel alignment is set using the vehicle’s control arms, knuckles, and frame.
► Factors affecting wheel alignment include camber, caster, steering axis inclination, toe-in and toe-out, scrub radius, toe-out on turns, turning radius, thrust angle, and ride height.
► Positive camber refers to the top of tires tilting away from the vehicle; negative camber refers to the top of tires tilting toward the vehicle; zero average camber refers to no tire tilt.
► Caster refers to the angle formed between the centerline of steering axis and true vertical, or the forward/backward tilt of the ball joints.
► Steering axis inclination (SAI) provides the front wheels with a self-centering function; it is formed by drawing a line through the upper and lower pivot points of the suspension assembly.
► Scrub radius (steering offset) is the distance between the center point of the tire contact patch at the road surface and the point of steering axis centerline contact with the road.
► The Ackermann principle ensures that the inner wheels turn at a sharper angle than the outer wheels when turning.
► Thrust angle refers to the relationship of the rear wheels to the vehicle’s imaginary centerline.
► When performing a wheel alignment, be sure to check front and rear cradle, thrust angle, wheel set-back, wheel camber, caster, toe, SAI, and toe-out on turns.
► There are three basic types of wheel alignment: two-wheel alignment, thrust-angle, and four-wheel alignment.
► Common issues related to the suspension system are vehicle wander, drift, pull, hard steering, bump steer, torque steer, and steering return concerns.
► Tools commonly needed to diagnose suspension or wheel alignment issues are the wheel aligner, ramp, turntable, wheel clamps, specification charts, workshop manuals, specialty alignment tools, dial indicators, measuring tapes, scan tools, general hand tools, various lift devices, air ratchets, and wheel braces.
► A common suspension system problem is excessive play in the parts, usually from wear in the joints and bushings.
► Common tools for maintenance and repair of suspension systems include those used in diagnosis as well as the following: component compression devices, levers, spring compressor tools, a strut-servicing tool kit, a universal strut nut wrench kit, and a 24-mm strut rod socket.
► Wheel alignment servicing equipment is used to measure the steering and suspension alignment angles.
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► As the transmission wears, it may begin to develop concerns for the customer such as popping out of gear, making growling noises, or becoming difficult to shift.
► A transmission that has been run low on gear oil will wear extremely quickly and will result in the need for rebuilding or replacement.
► Rebuilding a transmission/transaxle can be a large undertaking considering its complexity and all of the makes and models produced for the automotive market.
► The most important part in any rebuild/overhaul is to pay attention to detail and make sure you locate the cause/s of a transmission/transaxle failure, such as worn synchronizer rings, broken detent spring, worn bearing.
► Some special tools and equipment may be required to disassemble and reassemble today’s modern manual transmissions, such as special pullers or electronic devices.
► Failures inside the transmission can simply indicate replacement of wear items such as seals, gaskets, bearings and synchronizer blocker rings or the failure of hard parts, such as input, output, or counter shafts, gears, and synchronizer assemblies.
► The rebuilding of a transmission/transaxle is not something to be performed by a novice technician without any training.
► Among the first things to consider when doing any kind of service to a manual transmission/transaxle is obtaining and reading all manufacturer publications and service information.
► If it is necessary to disassemble a manual transmission because of an internal problem, a complete and thorough diagnosis is warranted in order to affect a complete and error free repair.
► Once the concern is fully understood, the technician needs to verify the concern, usually by test driving the vehicle, and diagnose the possible causes.
► The purpose of the powertrain mounts (motor mounts), is to support the engine and transmission/transaxle as it is placed in the car.
► It is always a good practice to inspect powertrain mounts whenever the vehicle is on the lift or if the customer complains of unusual shifting or noises present.
► Although a manual transmission/transaxle is being shifted manually, there is a bit of electronics used in the process of selecting gears on some transmissions.
► When overhauling a transmission/transaxle, all transmission case components should be cleaned and inspected to make sure that they can be reused.
► You have an important cost analysis job to perform for the customer.
► When rebuilding a transmission/transaxle, it is always a good practice to replace the gaskets and seals.
► Before replacing the gaskets, clean all gasket surfaces to make sure that the surface will accept the gasket and prevent leaks.
► The transmission/transaxle mating surfaces such as the main case and output shaft housing should be checked with a straight edge and feeler gauge to make sure that both surfaces are flat to ensure a tight seal.
► The front bearing retainer and the main transmission/transaxle case is another area that should be checked with a straight edge and feeler gauge.
► The shift tower surface is also an area to consider and check for flatness with a straight edge and feeler gauge as this may cause a leakage of fluid.
► When overhauling a manual transmission, it is important to inspect the synchronizer assemblies for damage before reusing them.
► A good place to start when inspecting for synchronizer wear and damage is when you drain the transmission fluid from the transmission/transaxle.
► Any gold colored particles may indicate that the blocking rings are excessively worn and may need to be serviced.
► The oil slinger should be inspected for any defects or damage such as scratches or bending of the slinger that might have occurred during the transmission failure.
► During a rebuild, it is always good practice to inspect or replace the oil pump parts if equipped.
► To prevent failure in the future, it is always a good practice to inspect and service the shift mechanism when rebuilding a transmission.
► Shift linkage adjustments that were present, will have to be performed again since the shifter cables or linkages will have to be loosened.
► Sometimes it is necessary to remove the transaxle final drive, whether there was a failure or for service because of a noise problem emanating from that particular area, such as gear or bearing noise.
► If it was found to be cheaper to use a replacement transmission, then the transmission may need to be reassembled for a core return to the manufacturer.
► When reassembling all components it is a good practice to lubricate parts as they are being installed.
► Endplay and preload adjustments are a necessary part of the disassembly and assembly of the transmission/transaxle.
► Endplay and preload adjustments can be an indicator of washer wear or bearing failure, which causes the shaft to walk back and forth in the case.
► Measuring endplay is critical to ensure that the transmission stays in service for a long time.
► It is highly important that the technician always follow the manufacturer’s service and maintenance procedures, as well as safety precautions.
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► Technicians must be EPA 609 certified to handle refrigerants.
► Performance testing of the air-conditioning system is one of the first steps in diagnosis.
► A performance test involves external cooling for the condenser, running the engine between 1200–2000 RPMs, placing the air-conditioning on max cold, the fan on high, and measuring the duct temperature, and then comparing the duct temperature to a system performance chart from the manufacturer.
► Servicing the air-conditioning system involves performance testing the system, diagnosing any issues, leak testing, identifying the refrigerant, reclaiming the refrigerant, performing any repairs, evacuating the system, recharging, retesting for leaks, and performance testing.
► Identifying refrigerant helps avoid mixing refrigerants, which cannot be reused and must be stored separately.
► Acid is formed inside an air-conditioning system when water is present.
► Acid test strips can be used to test for the presence of acid.
► An undercharged air-conditioning system contains less refrigerant than the system calls for.
► The one rule for diagnosis of an air-conditioning system is “when in doubt, suck it out.”
► The compressor is the most common source of abnormal noises arising from the air conditioner.
► If the high-side pressures are too high and the system is not cooling well, check the air flow through the condenser.
► Clearing the drain hose can clear up odors. If this does not work, an anti-odor kit may be required.
► Confirm the refrigerant in the system by using a refrigerant identifier.
► The air distribution system is designed to circulate air through the heating and cooling system, then into the passenger cabin.
► Refrigerant must be tested for acidic contaminants and water intrusion.
► Charge refers to the amount of refrigerant in the air-conditioning system.
► The TXV system is more sensitive to low charge (low refrigerant level) than the fixed orifice tube system.
► Components of a heating system include: radiator, thermostat, water pump, upper and lower radiator hoses, heater core, and heater control valve.
► Steps to the diagnosis and repair of air-conditioning systems are pretest and inspection, leak test, reclaiming refrigerant, problem repair, evacuation, charging, and post-testing.
► The two most common air-conditioning customer complaints are: the system is not working or the system has an unusual smell.
► Problems with air-conditioning system performance may be due to system leaks, compressor failure, or system blockages due to debris or frozen moisture.
► Variable factors, such as weather, air moisture content, temperature, condition and type of vehicle, and color and size of vehicle, all affect air-conditioning system functioning.
► Air-conditioning performance testing should be done before and after a repair.
► Air-conditioning system inspection should include possible condenser airflow restrictions, evaporator housing water drain, air filter, hoses and belts, coolant pressure, radiator cap vacuum and pressure, cooling fan, fan clutch, fan shroud, air dams, and heater control valves.
► Air-conditioning systems are equipped with protective devices designed to shut down the system if the pressure becomes elevated.
► Tools needed to maintain and repair air-conditioning systems include: sealant detector, reclaim/recycle machine, refrigerant identifiers, pressure gauge sets, air-conditioning machine, anemometer, retro fit kit, pressure-temperature chart, vacuum pump, electronic leak detector, dye leak detector, oiler, vacuum gauge, micron gauge, and line wrench.
► Methods of leak testing are sniffer testing, dye testing, and nitrogen testing.
► Refrigerant leaks can be detected by sniffers via ultra-sonic, heated diode, or corona-suppression.
► Any time the air-conditioning system is opened, the refrigerant must be recovered (reclaimed).
► The air-conditioning system should be flushed if the compressor comes apart, the desiccant bag breaks open, or the oil is contaminated.
► Use caution when removing and installing a TXV to avoid creating leaks.
► Following a repair, the air-conditioning system should be evacuated via an air-conditioning machine or air-conditioning gauges and a vacuum pump.
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► The primary components of the battery are the case, cover, vent caps, plates, separators, electrolyte, and terminals.
► Batteries operate by storing electrical energy in chemical form.
► The discharge of electrolytes produces battery current.
► The standard automotive battery has 2.1 volts per cell, with six cells holding 12.6 volts on a fully charged battery.
► Batteries are classified into groups, and only certain groups and layouts will fit certain vehicle applications.
► Batteries are rated by electrical capacity, cold cranking amps, and amp hour ratings.
► There are two chemicals that make the battery a safety hazard: hydrogen gas and sulfuric acid.
► The absorbed-glass mat battery is good for rough handling and can be mounted on its side compared to the electrolyte battery.
► Battery temperature plays a critical part in battery life. When a battery is cold, it takes more power to start the vehicle; when a battery is to hot, its life is diminished significantly.
► Lithium-ion batteries are the future and are especially being used in hybrids. However, they have not replaced the conventional battery in most applications.
► There are two ways to connect the battery to the vehicle: the top-post design and the side-post design.
► Batteries must be kept free of corrosion, as corrosion is the fastest way to destroy a battery and cable.
► If a vehicle seems to have a dead battery after sitting, the battery needs to be checked for parasitic draw.
► Jump-starting a vehicle is one of the simplest automotive tasks to perform, but done incorrectly, it can cause battery and possible vehicle damage. Always ensure the proper polarity when connecting the dead and good batteries together.
► When servicing a battery, always wear the proper personal protective equipment.
► Battery maintenance requires inspecting, cleaning, testing, and charging. Always follow all applicable technical data when performing battery maintenance.
► Batteries need to be recycled once their life cycle is used up. They contain hazardous materials that cannot be put in a landfill.
► The best way to test a battery’s capacity and internal condition is through a battery load test.
► The starting system provides a method of rotating (cranking) the vehicle’s internal combustion engine (ICE) to begin the combustion cycle.
► The starting system consists of a battery, cables, a solenoid, a starter motor, a ring gear, and an ignition switch.
► The starter motor converts electrical energy to mechanical energy.
► Some starters operate through gear reduction, giving the same amount of torque at less size and weight.
► A starter motor is basically an electromagnet.
► The starter motor pinion must mesh with the engine ring gear to turn the engine over and allow the vehicle to start.
► Once the engine starts running on its own, the starter must disengage from the ring rear to avoid damaging the starter or the ring gear.
► The solenoid on the starter motor performs two main functions: It switches the high current flow required by the starter motor, and it engages the starter drive with the ring gear.
► Vehicle immobilizers generally comprise a computer-managed security system that disables the start and engine systems by using an electronic system to uniquely identify each vehicle key by a security code system.
► Hybrid vehicles use both an ICE and electric motors to power the vehicle’s drive train.
► Testing starter motor current draw is a good indicator of overall starter motor performance.
► Compared to older vehicles, newer vehicles put a higher demand on the charging system, as many systems are required not only to operate the vehicle but also to operate an array of entertainment systems.
► The DC generator has not been used on vehicles since the 1960s.
► The AC generator, or alternator, is used on today’s vehicles both to recharge the vehicle battery and to run numerous other electrical accessories on the vehicle.
► The alternator converts mechanical energy into electrical energy.
► The alternator changes AC to DC by using a rectifier with diodes to allow electrical current to flow in one direction only.
► The alternator has a regulator, either built in or external, to keep the alternator from overcharging the battery.
► The more amps the alternator can produce, the more accessories the vehicle electrical system can handle.
► The first item that should be checked if an alternator is not charging according to the manufacturer’s specifications is the belt tension and condition.
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► Functions of the cylinder head include: admit air and fuel to combustion chamber, release exhaust after combustion, and allow coolant to flow around the top of the combustion chamber.
► The cylinder head forms the top of the combustion chamber and is securely fastened with a head gasket between the head and block.
► Cylinder heads may be aluminum alloy (lighter weight, boosts fuel economy) or cast iron (heavier, but lower engine operating temperatures).
► Engines may be overhead valve, overhead cam, or dual overhead cam.
► Cylinder head parts include: base cylinder head casting, intake valves, exhaust valves, valve keepers, valve retainers, valve springs, oil seals, coolant seals, rocker arms, plugs, and camshaft.
► Cylinder heads are designed to improve the swirl and turbulence of the air/fuel mixture moving into the combustion chamber.
► A hemispherical (HEMI) combustion chamber has intake and exhaust valves located on opposite sides to create cross flow of gasses.
► The amount of air an engine can take in and remove is referred to as “breathing.”
► The greater the air/fuel mixture, the more heat is generated, and thus more engine power.
► Dual overhead cam engines often have multivalve cylinder heads to create quicker, more efficient air/fuel movement.
► Cylinder head shapes can be oval (bathtub), wedge, hemispherical, or gas direct injection (GDI).
► Smaller intake and exhaust ports are generally better for engines that operate at low speeds (4-wheel drive), while larger intake and exhaust ports are ideal for engines operating at high speeds.
► Components of the valve train are driven from the camshaft and include: lifters, push rods, rocker arms or cam followers, valves, valve springs, keepers, and retainers.
► Components of the valve are: valve tip, keeper grooves, valve stem, valve face, and valve margin.
► Valves are located in the cylinder head and are configured in two-, three-, four-, and five-valve arrangements.
► Most engines are fitted with poppet (mushroom) valves.
► Exhaust valves are designed to withstand higher temperatures than intake valves.
► Valve guides are integral (non-replaceable) or non-integral (replaceable) and are designed to limit a valve’s movement to up-and-down and retain lubrication for the valve stem.
► Valve stem seals are designed to prevent oil leakage; the three basic types are umbrella style, O-ring, and positive.
► Valve seats form a strong seal with the valve face and must withstand high temperatures and extreme pressure.
► Valve train refers to all the parts that contribute to the opening or closing of the intake and exhaust valves.
► Types of valve trains correspond to engine types: overhead valve, overhead cam, or dual overhead cam.
► Rocker arms are categorized by the ratio of movement on the valve side to movement on the push rod side.
► Push rods, found in overhead valve engines, transfer the motion from the valve lifter to the rocker arm; push rod types are: ball-to-ball, ball-to-cup, and ball-to-adjustable tip.
► Lifters can be solid (manually adjusted) or hydraulic (self-adjusting) and are located in the engine block, cylinder head, rocker arms, and between the cam and valve tip.
► Camshaft followers are used in overhead camshaft engines in place of rocker arms.
► Bucket-style lifters transmit movement from the cam lobe to the tip of the valve.
► The valve spring is designed to close the valve and exert pressure to hold it firmly against the valve seat.
► Valve-spring retainers and valve locks (keepers) hold the valve spring in place.
► Gaskets are designed to create a seal when compressed between two stationary parts.
► Gaskets are single use only and must withstand engine heat.
► Functions of a head gasket are to seal and contain combustion pressure, seal oil passages, and control coolant flow.
► Anisotropic head gaskets conduct heat laterally.
► Oil seals can seal the rotating parts of an engine and are made of rubber or a rubber-type compound comprised of silicone, EPDM, or other flexible material.
► The lip-type dynamic oil seal is the most commonly used type.
► O-rings are used to seal stationary or slowly rotating shafts.
► Sealants are designed to seal together two surfaces in stationary contact with one another.
► Always check manufacturer recommendations for the proper type of sealant.
► Common cylinder head problems include: wear, cracks, leaking coolant or compression gasses, warped cylinder head, burnt or warped valves, and stripped spark plug hole threads.
► Thermal stress is the main cause of cylinder head cracks.
► Many cylinder head repairs require the skill of a certified machinist.
► Only remove the cylinder head after extensive testing and certainty that removal is required.
► Always clean the cylinder head after removal.
► Test valve springs for squareness and measure both spring height and installed pressure.
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► The power steering system can be either a hydraulic or electric type.
► A basic steering system has four main parts: a steering column, a steering box, a steering linkage, and a steering knuckle.
► Steering geometry is a geometric arrangement of linkages in the steering of a vehicle, designed to keep the wheels properly oriented through various positions of the steering and suspension systems.
► The rack-and-pinion steering system is used on the majority of front-wheel drive vehicles because of the space restriction under the hood.
► The parallelogram steering system is used on larger vehicles where ride comfort is more important than sporty handling.
► When servicing the steering column, it is good practice to disarm the triggering system for the driver’s side airbag. If not properly disarmed, it could trigger accidentally.
► Because of the critical nature of the airbag, it is imperative that it is always connected electrically to its control module, so it can be deployed when needed.
► The function of all steering boxes, whether manual or power, is the same: to transfer the rotary motion of the steering wheel into the side-to-side motion needed to make the wheels pivot left and right.
► There are two basic types of steering boxes: those with rack-and-pinion gearing and those with worm gearing and a sector shaft. In both types, the gearing in the steering box makes it easier for the driver to turn the steering wheel and, hence, the wheels.
► Four-wheel steering means the rear wheels can be steered independently of or in conjunction with the front wheels. There are two types: active and passive.
► There are three types of power steering: hydraulically assisted power steering, electrically powered hydraulic steering, and fully electric power steering.
► Electrically powered hydraulic steering replaces the customary drive belts and pulleys that drive a power steering pump in a conventional rack-and-pinion steering system with a brushless motor.
► The steering sensor performs two functions: First, as a torque sensor, it converts steering torque input and direction into voltage signals for the ECU to monitor. Second, as a rotation sensor, it converts the rotation speed and direction into voltage signals for the ECU to monitor.
► Higher voltage electrically assisted power-steering systems were developed for modern hybrid vehicles. The higher voltage battery system of the hybrid vehicle provides all the power, with no reliance on engine or hydraulic power.
► Many of the problems associated with steering system are mechanical, but as more EPS systems are produced, electrical faults are becoming more common. The main problems that arise in the steering system are play and hard steering; common causes are wear and poor lubrication.
► Power steering fluid is critical to the proper functioning of the entire steering system. Any leak, no matter how small, is cause for repair.
► To maintain a safe-operating vehicle, regular inspection of the steering components is essential.
► Pressure testing the power steering system is performed when the driver complains of hard steering or when there are repeated hose failures.
► Removing and replacing the rack-and-pinion steering gear should be considered only after examining all parts of the steering system and performing a full diagnosis to ensure the problem is not the result of some other fault.
► Checking tie-rod ends is important in identifying steering problems because the ends are frequently damaged or worn.
► On vehicles equipped with EPS, the electric power assist system should be tested any time the driver complains of steering difficulties, either hard or loose.
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► Without a set of gears, flexible joints, and shafts to transfer the power from the engine and transmission, the vehicle would not be able to propel itself up hills, handle turns, or hold itself back as it goes down hills.
► In a conventional rear-wheel drive vehicle, the engine and transmission are mounted longitudinally at the front.
► Vehicles with rear- or mid-mounted engines normally use a transaxle and transfer the drive to the road wheels by independent half-shafts.
► The front-engine front-wheel drive vehicle typically, but not always, uses a crosswise-mounted (transverse) engine coupled to a transaxle.
► CV joints allow for smoother transfer of power and allow for the vehicle to turn more tightly without the joint binding.
► CV joints are most often used on the half-shafts of front-wheel drive vehicles and may be mounted at the end of the drive axles in some rear-wheel drive vehicles.
► The most common type of joint is the universal joint or simply “U-Joint” (the correct term for it is a Hooke’s joint).
► The driveshaft itself allows power transfer from one component to another such as from the transmission output shaft to the differential and drive axles.
► The rear-wheel driveshaft transfers the power from the transmission to the final drive at the rear of the vehicle.
► Since the maximum length of a driveshaft is approximately 72" (183 cm), to prevent twisting from the torque output, two or more sections may be used.
► The front section of the two-piece driveshaft is supported at its rear end by a center bearing, called the carrier bearing.
► The U-joint is capable of working at a maximum angle of 3 degrees; beyond this, vibration and damage will result from U-joint binding.
► When working with a two-piece driveshaft or a splined driveshaft, it is critical that the yokes of the driveshaft (the portion of the shaft that has the holes in it for the U-joint end caps to fit into) line up with each other from one end of the driveshaft to the other.
► In front-wheel drive vehicles, the driveshafts transfer the drive directly from the differential inside the transaxle to the front wheels.
► A front-wheel drive transaxle typically does not place the differential directly in the center of the vehicle; instead it is offset to one side since it is bolted to the end of the transversely mounted engine.
► Torque steer is caused by the flexing of the longer half-shaft, resulting in lower torque to one side than the other, creating the pulling condition. To combat this condition, many manufacturers use an intermediate shaft.
► The differential provides the means of transferring power from the driveshaft (propeller) to the drive wheels, while allowing the vehicle to turn smoothly.
► Final drives can be found in axles either at the front or rear of the vehicle or can be found in the transaxle of a front-wheel drive vehicle.
► A ring gear and pinion gear located in the final drive transfer power through 90 degrees and provide a final gear reduction to the driving road wheels.
► The transfer case or power take-off (PTO) allows the transfer of power to the front and rear axles.
► Limited slip differentials allow normal differential action under normal driving conditions, but when road conditions are not normal, the limited slip differential reduces or prevents differential action so that a wheel cannot spin freely.
► Helical-geared limited slip differentials respond very quickly to changes in traction. They also do not bind from friction in turns and do not lose their effectiveness as wear develops in the clutch-style units.
► There are different final drive setups. Some are semi-floating and others are full floating axle assemblies. The difference is how they are attached to the final drive.
► The purpose of axle seals is to maintain the required amount of oil in the differential to maintain quiet operation of the differential and related parts and to ensure lubrication for the bearings and gears.
► The transmission control module (TCM) manages line pressures, shift functions, etc., and even incorporates a “self-healing” adjustment capability, along with the ability to memorize driver preferences/behaviors.
► Proper diagnosis of vibration, noise, and other problems can keep a vehicle running and lasting longer. Always ask clarifying questions when a customer complains of noises or vibrations.
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► Automatic transmissions are now standard equipment in vehicles.
► Automatic transmissions contain planetary gear sets.
► Automatic transmissions have four or more forward gear ratios and one reverse ratio.
► Typical forward gear ratios are as follows: first gear, 3:1; second gear, 1.75:1; third gear, 1:1; and fourth gear, 0.80:1.
► Adding more gear ratios to the transmission boosts fuel economy.
► Automatic transmissions select and shift gears without driver input and can couple or uncouple from the engine as necessary.
► Types of automatic transmissions include conventional, transaxle, dual clutch, continuously variable, dual shaft, and hybrid (series or parallel).
► Conventional automatic transmissions have planetary gear sets, connect to the engine via torque converter, and use holding devices to stop one or more parts of the planetary gear.
► Transaxle transmissions add a differential and final drive gear to a standard transmission.
► Dual-clutch transmissions use two wet clutches instead of a standard torque converter.
► Continuously variable transmissions use two moveable pulleys rather than typical gears.
► Honda and Saturn vehicles use dual-shaft transmissions that have a main shaft and a countershaft, as well as multidisc clutch packs.
► Hybrid vehicles often use series transmissions, in which an electric motor supplements power to the transmission.
► A hybrid vehicle may use a parallel hybrid transmission, in which either the engine or an electric motor can power the transmission.
► Automatic transmission gears are typically helical (most commonly used), spur (straight cut), or hypoid.
► Planetary gear sets use either helical- or straight-cut gears and are comprised of three components: planet carrier, sun gear, and ring gear.
► Bands, multidisc clutches, and one-way clutches are the three basic holding devices used in transmissions.
► Automatic transmission fluid (ATF) transfers heat from the internal transmission components to the transmission cooler.
► ATFs are oil-based or synthetic and may contain these additives: rust and corrosion inhibitors, friction modifiers, seal conditioners, detergents, antifoam, and viscosity modifiers.
► Components of an automatic transmission include the front pump; flex plate and ring gear; front pump seal, bushings, and pump drive; case, extension housing, and pan; gaskets and seals; and parking pawl assembly.
► The front hydraulic pump ensures a continuous pressurized supply of fluid to the transmission.
► The four types of automatic transmission front pumps are gear/crescent, rotor, vane, and variable displacement.
► On automatic transmissions, the flywheel is replaced with a flex plate, with a ring gear wrapped around the outside edge.
► Gaskets may be made of paper, fiber, cork, or neoprene (which may be reusable).
► Types of internal seals include square cut, lip, locking, O-ring, and Teflon.
► Compound planetary gear sets are used to create all the ratios needed for modern vehicle travel.
► Two types of compound planetary gear sets are Simpson and Ravigneaux.
► Thrust washers and thrust bearings are used to control forward and backward motion of transmission components.
► Bushings should be checked during transmission overhaul; the front pump bushing or the output shaft bushing will likely need replacing.
► Automatic transmission brake bands use friction material and servo pressure to stop the drum from spinning.
► Multidisc clutches are used to couple planetary gear members to input shaft, output shaft, or the case.
► Clutch release may be assisted via a large coil spring, a pack of small springs, or a diaphragm spring.
► Check clutch pack clearance when rebuilding an automatic transmission.
► A torque convertor works with the transmission to select the proper gear to meet the speed and power demands of the vehicle.
► A single-stage torque converter contains an impeller, a turbine, and a stator.
► Torque multiplication is a state that occurs when the impeller is turning substantially faster than the turbine. The greater the difference in speed the greater the torque multiplication.
► A torque converter clutch is used to lock the turbine to the impeller when the vehicle is operating under light loads, to improve fuel economy.
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► Climate control systems can be manual, semiautomatic, or automatic.
► Manual climate control systems give the driver full control over blower motor speed, temperature of outlets, and direction of airflow.
► Semiautomatic control systems use an A/C ECU to turn on or off the A/C compressor, while the driver controls temperature request, blower motor speed, and airflow position.
► In automatic control systems the driver selects a temperature and the A/C ECU manages the subsystems necessary to achieve that temperature (heat, A/C, and air distribution).
► The A/C ECU requires input from electronic sensors to determine: vehicle heat load; desired temperature setting; and the temperature of ambient air, cabin air, evaporator, and engine coolant.
► An electric actuator or a vacuum servo may be used to move air box doors.
► Components of a climate control system include: blower motor, air box, heater core, evaporator, actuator, and control head.
► The blower motor is attached to a circular fan and provides the desired amount of airflow to the vehicle cabin.
► The doors that control airflow include: blend door, mode door, and recirculation door.
► A potentiometer is a three-wire sensor that signals the position of the blend door to the A/C ECU.
► A negative temperature coefficient thermistor (temperature sensor) gains resistance as the temperature drops, while a positive temperature coefficient thermistor loses resistance with lowered temperatures.
► Actuator feedback signals may be in the form of voltage signals.
► A pulse width modulation refers to a pulsing current flow that controls a blower motor’s speed and provides an infinite number of speeds.
► The sun load (or solar) sensor is a photo diode that reads light entering the windshield of the vehicle.
► The air conditioning pressure sensor monitors refrigerant pressure.
► The evaporator temperatures sensor ensures that the evaporator maintains the correct temperature by controlling compressor cycling.
► Control panels vary according to car type and A/C ECU system. Panels may have rotary switches, recirculation buttons, auto mode, or digital temperature display, and systems may offer dual temperature control or rear-climate control.
► Control panel assemblies may be mechanical or automatic. Mechanical systems may operate cables, vacuum valves, or electrical switches.
► The blower motor speed is determined by resistors connected to the fan control switch that feed voltage to the motor.
► In some vehicles the highest blower motor speed receives a full 12 volts from a dedicated fan relay.
► The A/C compressor is turned on/off by the A/C compressor cultch.
► Components of a compressor clutch include the pulley, clutch coil, compressor shaft, and a shim.
► Hybrid cars may use a standard A/C compressor clutch arrangement or may use a dual-drive A/C compressor.
► Common HVAC system issues are: electric actuator failure, vacuum hose failure, and sensor failure.
► Vehicles with HVAC systems equipped with self-diagnostics will provide a diagnostic trouble code that can help determine the cause of system failure.
► Use manufacturers’ troubleshooting charts when diagnosing HVAC controls malfunctions.
► Electrical malfunctions in HVAC systems may be due to failure of actuators, switches, connectors, wiring, grounds, or may be due to pin fit issues.
► Consider using an infrared thermometer to check coolant temperature without removing the radiator cap.
► Inspect and test blower motors for foreign objects, shorted motor, or binding of the fan motor shaft.
► Possible causes of the compressor clutch control system not working are: bad clutch coil, electrical fault in control circuits, large clutch air gap, or low refrigerant level.
► Inspect and test the heater control panel assembly and control cables if the system is not delivering proper air temperature.
► Air conditioning systems can grow mold and bacteria from trapped condensed moisture, which can then give off an unpleasant odor, necessitating use of an anti-odor kit.
► Tools needed for inspection, maintenance, and repair of an HVAC system include: infrared thermometer, digital volt ohm meter (DVOM), back probes, fused jumper wire, and a scan tool.
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► Braking systems evolved from scrub brakes to band brakes to the drum and disc brakes that are used today.
► Electronic brake systems use computer technology to assist with braking by determining speed and needed force to stop.
► The development of electronic brake systems has led to improvements in consumer safety and fuel economy.
► Brake-by-wire systems use computer technology in place of the mechanical or hydraulic connection between the brake pedal and wheel brake units.
► Regenerative brake systems (used in hybrid vehicles) convert a vehicle’s energy into electrical energy, which is stored in the battery for later use.
► Factors affecting the effectiveness of braking systems include road surface, road conditions, vehicle weight and height, load on wheels, type of tire, and aggressive vs. defensive driving.
► Every vehicle has two brake systems: service brake (for stopping the vehicle in motion) and parking brake (for holding the vehicle when stationary).
► Hydraulically operated braking systems use a system of cylinders to transfer pressure from the brake pedal to the wheel.
► The braking system converts a vehicle’s kinetic energy (the energy of an object in motion) into an alternate form of energy (e.g., heat).
► Acceleration and deceleration determine whether the vehicle’s speed is increasing or decreasing. Both require an outside force for action, such as the vehicle’s engine (acceleration) or braking system (deceleration).
► The law of conservation of energy requires that energy must be transformed from one form to another; it cannot be created or destroyed.
► Standard brakes use friction to create resistance, thus transforming kinetic energy into heat energy.
► The amount of force pushing two surfaces together compared to the amount of resistive force generated between the two surfaces sliding against each other is called the coefficient of friction.
► Heat energy created by the braking process gets dissipated into the atmosphere.
► Reduction in a vehicle’s stopping power (brake fade) can be caused by heat fade, water fade, or hydraulic fade.
► Braking systems create rotational force on the vehicle’s suspension, resulting in weight transfer to the front wheels.
► There are three types of levers: lever of the first order (fulcrum in the middle), lever of the second order (load in the middle), and lever of the third order (effort in the middle).
► Engine braking allows the engine to act as a brake by absorbing energy during deceleration.
► Technicians can be held liable for improperly repaired brakes.
► Disc brakes and drum brakes are two types of friction brakes that are used on lighter vehicles; both can be equipped with antilock braking systems.
► Air-operated braking systems, used on heavier vehicles, use air pressure to apply the brakes (drum or disc style).
► An exhaust brake may be used in addition to friction brakes in heavy vehicles and creates engine pressure by restricting the exhaust flow.
► Jake brakes are used in heavier diesel vehicles and rely on compression to slow the crankshaft and increase braking effectiveness.
► Trailers over a certain weight often use an electric braking system to give the driver braking control.
► Parking brake styles include: top hat parking brake, drum-style parking brake, and transmission-mounted parking brake.
► Parking brakes use a ratcheting mechanism to maintain tension on the parking brake cables and assembly when applied.
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► The intake system ensures that clean, dry air is delivered to the engine to be mixed with fuel.
► Clean air is essential to a long-lasting engine.
► The intake system ensures that air and fuel are delivered to the engine efficiently.
► The primary components of the intake system are the intake manifold, the throttle body, and the air induction system.
► There are two types of intake manifolds: wet and dry.
► The air induction system consists of the following components: an air cleaner and housing, solid and flexible-duct tubing, and connectors.
► Ducting can be made of plastic for movement and connects the air cleaner to the intake manifold.
► The intake manifold provides a path for fuel and air to travel to the engine combustion chambers.
► Volumetric efficiency compares the volume of air entering a cylinder during intake to the internal swept volume of the cylinder when the piston is at bottom dead center.
► Back-pressure typically should never get higher than 3 psi (20.7 kPa). If it is greater, it can create poor performance issues, as it will cause exhaust to back up into the combustion chamber, minimizing the fresh airflow into the engine.
► Forced induction increases air pressure in the intake manifold above atmospheric pressure.
► A supercharger compresses the air intake to above atmospheric pressure, which increases the intake air density to the engine.
► A turbocharger is a forced induction system that uses wasted kinetic energy from the exhaust gases to increase the intake pressure.
► When using a turbocharger, exhaust gases turn the turbine, which in turn pulls in fresh air at a higher rate than normally aspirated engines.
► When air is compressed, it heats up; to keep the heating process to a minimum, an intercooler is used to cool the air prior to being injected into the engine.
► The exhaust system involves many components that work together to remove the by-products of combustion from the engine.
► The primary components of the exhaust system are the exhaust manifold, engine pipe (sometimes called the down pipe), catalytic converter, intermediate pipe, muffler, tailpipe, and exhaust brackets.
► The exhaust manifold provides a path for exhaust gases to escape the engine. In a high-performance engine, headers are tuned for better engine breathing.
► The flexible connector allows movement between the engine and the rest of the exhaust system and keeps the pipes aligned under a load.
► A catalytic converter is used to convert unacceptable exhaust pollutants, such as carbon monoxide, certain hydrocarbons, and oxides of nitrogen, into less dangerous substances.
► There may be one or two heated oxygen sensors after the catalytic converter.
► The rubber exhaust brackets support the system and allow movement and dampening action in the exhaust system.
► The function of a vehicle’s muffler is to minimize the sounds coming from the exhaust system.
► The baffles in the exhaust system help to muffle the noises that the engine makes during normal operation.
► The tailpipe prevents the harmful exhaust fumes from entering the passenger compartment.
► Gaskets are used throughout the exhaust system to make a tight, leak-free system.
► The throttle body and the induction system ensure that the engine gets airflow into the cylinders and must be inspected for proper operation.
► Refer to applicable manufacturer’s information when inspecting the induction system or the exhaust system.
► An exhaust back-pressure test will reveal whether there is a blockage in the exhaust system that will affect engine performance or drivability.
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► Electrical systems on modern vehicles are becoming increasingly complex with the addition of a range of electronic and accessory systems, such as global positioning systems, entertainment systems, security systems, electric seats, and heated glass. Many of these systems are controlled by body computer systems.
► The controller area network (CAN-bus) and the bus system are used together in vehicle terminology (often called “CAN-bus”) to describe the data-sharing network in vehicles. The many sensors and engine control units or modules can share information across a common network using the CAN-bus protocol to communicate efficiently and effectively with low data loss.
► Diagnosing and repairing vehicles may require software transfers, software updates, or flash reprogramming of the vehicle’s electronic modules with the manufacturer’s latest update.
► Electric cooling fans for the radiator are increasingly common, particularly for transversely mounted engines and as supplementary cooling fans for vehicles equipped with air conditioning.
► Power mirrors use permanent magnet electric motors to control the up-and-down, in-and-out movement of the passenger’s and driver’s side mirrors.
► Electric windows use permanent magnet motors located in each of the passenger doors and sometimes in a rear door to control the up-and-down movement of vehicle windows.
► The sound of a horn is produced by the vibration of a metal diaphragm, which is operated by an electromagnet switched by a set of contacts.
► Technicians today need to know how to service all the accessories behind the door panels. This is a critical skill that must be mastered without damaging the accessory, wiring, or door panel.
► The wiper and washer system is an important vehicle safety system. The wipers ensure that the driver has a clear line of sight through the windshield by removing any excess moisture from the glass.
► In the basic cruise control system, the driver programs a set target speed and the cruise control system’s electronic control unit attempts to accelerate or decelerate the vehicle to maintain the target speed by commanding a throttle actuator to control the throttle butterfly.
► Active or dynamic cruise control systems adapt to the driving environment by sensing and adjusting vehicle speed based on changing conditions.
► Vehicle safety systems are designed to protect occupants during accidents; they can be classified as primary, or passive, systems and secondary, or active, systems.
► Seat belt pre-tensioners are used to tighten the seat belt in a severe frontal accident; both mechanical and electronic control systems are available.
► Crash sensors can be installed in various positions throughout the vehicle. Their location depends upon the direction of deceleration they are designed to detect.
► The global positioning system (GPS) relies on a group of at least 24 satellites orbiting approximately 12,600 miles (20,200 km) above the earth.
► Automotive telematics is a satellite-based system that combines two-way communication and information technology within the vehicle.
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► Preparation work necessary prior to engine assembly includes recleaning the engine block and crankshaft passages; ensuring piston, ring, and block clearances are within specifications; and determining the correct direction for piston installation on the connecting rod.
► Engine assembly includes:
► Check piston-to-cylinder wall clearance by using an outside micrometer.
► Check piston ring end gaps prior to installing piston rings.
► Piston pins are full-floating or semi-floating pins (wrist pins).
► It is a good idea to always perform a temporary test buildup of the rotating assembly (including cylinder heads and valve train).
► Ensure that main bearings are properly sized to the crank and that the bearing cap and saddle are clean and dry.
► Main bearing clearance must meet the manufacturer’s specifications and can be measured using an inside micrometer, outside micrometer, bore gauge, or Plastigauge.
► Check thrust bearing end play, as this controls crankshaft end play.
► Check rod bearing, internal, and piston-to-valve clearances.
► Two methods for checking piston-to-valve clearance are clay and dial indicator.
► The clay method clearance check uses a valve impression in clay to indicate where the valve and piston may have interference.
► The dial indicator method checks clearance at various piston positions.
► Paint the engine to protect it from rust and corrosion.
► Install new soft plugs and cleaned oil gallery plugs.
► Install the crankshaft, first ensuring that main bearings are clean and properly lubricated.
► Carefully install piston rings with any marks facing the correct way.
► Pistons can be installed after all piston prep work is finished, including properly positioning piston rings; lubricating pistons, rings, and cylinder walls; compressing piston rings; and lubricating connecting rod bearing inserts and rod journal.
► Check rod side clearance with a feeler gauge following piston and rod installation.
► Check the height of the piston to the cylinder block deck using a depth micrometer.
► Install the cylinder head(s) after ensuring the head and block are clean and dry.
► Use new torque-to-yield head bolts or ensure reusable bolts have clean threads.
► Ensure the head gasket is properly positioned and apply sealant if necessary.
► Torque head bolts to the manufacturer’s specifications.
► Install the timing belt (or chains) following cylinder head installation; ensure it is properly tensioned.
► Ensure timing marks on chains and belts are aligned according to the manufacturer’s specifications.
► Install the oil pump and oil pickup tube.
► Oil pickup tubes may be one of three types: screw in, bolt on, or press in.
► Only use adhesives and sealers that meet service requirements for the specific engine you are working on.
► Room temperature vulcanizing (RTV) silicone should not be used on neoprene gaskets with multi-sealing edges, but is safe for paper gaskets.
► Priming the engine will ensure all moving parts receive oil once the engine is started.
► The engine can be primed by spinning the oil pump with a drill attached to the pump drive or by using a pressure bleeder tapped into the engine oil galleries.
► The following external engine components should be installed in the proper order: manifolds, sensors, water pump, thermostat, alternator, balancer, power-steering pump, and air-conditioning compressor.
► The first external component to install is the intake manifold.
► Install engine accessories after installation of the external components.
► The final step is to visually inspect the camshaft and drive belt/chain assembly and to replace parts as necessary.
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► The manual transmission allows a driver to manually vary engine torque and output to the drive train.
► The ability of the technician to drive, service, repair, and maintain the manual transmission/transaxle is a critical skill.
► A manual transmission/transaxle allows the driver to directly vary the gear ratio by manual selection, between the engine and the driving road wheels.
► The components of a manual transmission can vary depending on the use and size of the transmission.
► The gear ratio is the number of turns of the input gear, necessary to achieve one turn of the output gear.
► Gear ratio theory will help you to understand how power is distributed and how power and speed varies as the vehicle travels.
► In keeping with the gear ratio theory, compound gear trains have two or more pairs of gears in constant mesh, so that they rotate together and are found inside the transmission/transaxle.
► In direct drive rotation, both the output and input gears turn at the same speed, and the turning effort of the output gear will equal the effort applied by the input gear.
► All gear boxes have shift rails and shift forks. The gear shift lever/mechanism can be located on the top, on the side or on the column.
► The interlock mechanism is the device that ensures two gears cannot be selected at the same time.
► Many newer manual transmissions are equipped with Electronic Reverse Lockout systems, which use an electronic solenoid to prevent the transmission/transaxle from being shifted into reverse while the vehicle is in forward motion.
► In a manual transmission/transaxle, the gears and shafts are supported on bearings or bearing surfaces to reduce rolling friction.
► Roller bearings are used to support radial loads.
► Caged roller bearings can be used to support gear rotating on an output shaft.
► Thrust washers act as wear surfaces and can be used to adjust end-play.
► Tapered roller bearings are used to sustain radial and thrust loads.
► Transmission problems include nose, hard shifting, jumping out of gear, no gear selection, and fluid leaks.
► Lubrication type and condition are critical factors in transmission performance and reliability.
► Having the gearbox and final drive gears in one casing provides a compact and relatively quiet unit and fits well into front wheel drive vehicles.
► Historically, manual transmissions have not required the use of electronics, but as with all vehicle systems, electronics are starting to play a more common role.
► Manual transaxles problems can be diagnosed with the guidance of the manufacturer’s diagnostic tables.
► A simple issue that can cause hard shifting is created by maintenance work that is performed improperly on a manual transmission/transaxle.
► Always adjust shift linkage following the manufacturer’s methods.
► Always refer to the manufacturer’s prescribed maintenance schedules and fluid changes to ensure the unit lasts the life of the vehicle.
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► Vehicles under repair must be protected from further damage occurring while in the shop.
► A preservice vehicle walk-around will ensure that the shop and customer are in agreement about existing damage to the car.
► Use protective equipment, such as seat covers, floor mats, and fender covers, to prevent damage and to protect vehicles against grease, oil, and dirt.
► Use specified containers for corrosives and grease; clean up spills thoroughly.
► Carefully use tools and jacking or hoisting equipment to prevent mechanical damage to a customer’s car.
► Only experienced, licensed drivers should test-drive high-performance vehicles.
► Moving cars in and out of the shop is another opportunity for damage to occur.
► Inspect protective covers (fender covers and floor mats) for existing damage prior to use.
► The safe working load indicates the operating capacity for lifting equipment.
► Lifting equipment includes vehicle hoists, floor jacks, jack stands, engine and component hoists, chains, slings, and shackles.
► Periodically check and test lifting equipment; consult the test certificate if available.
► Vehicle jacks can be classified by the type of lifting mechanism they use: hydraulic, pneumatic, or mechanical.
► Jack types include floor jacks, high-lift (farm) jacks, bottle jacks, air jacks, scissor jacks, sliding bridge jacks, and transmission jacks.
► Jack stands support a vehicle’s weight when it has been raised; always use jack stands in pairs.
► Vehicle hoists raise the vehicle to allow technicians underside access.
► Vehicle hoists are most commonly single-post, four-post, or two-post.
► Never use a vehicle hoist without activating the safety lock or for lifting a vehicle heavier than the rated limit.
► Engine hoists can lift heavy objects out of a vehicle and onto an engine stand.
► Vehicle inspection pits allow access to the vehicle’s underside without using a hoist or jack.
► Cover or fence inspection pits when not in use to prevent others from falling in.
► Choose vehicle jacks according to size and lifting capacity.
► Do not use a vehicle hoist if the vehicle’s frame is not structurally sound.
► Make sure a vehicle has enough clearance over the lifting mechanism.
► Check for damage before using an engine hoist, and make sure all components have the lifting capacity needed for the task.
► Clean the vehicle and remove tools and vehicle protection before returning it to the customer.
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► The five events common to all internal combustion engines are intake, compression, ignition, power, and exhaust.
► A four-stroke cycle engine completes the intake, compression, power, and exhaust strokes in two revolutions of the crankshaft.
► A two-stroke cycle engine completes the intake, compression, power, and exhaust strokes in one revolution of the crankshaft.
► The diesel fuel system consists of a lift pump, a fuel filter and water separator, a fuel injection pump, and high-pressure lines and nozzle holder assemblies.
► Today’s engines use high-pressure common rail injection systems to meet rigid emission standards.
► Three phases of combustion are ignition delay period, flame spread, and direct burning.
► Diesel engine components are exposed to higher operating temperatures, pressures, and forces than gasoline engine components.
► Both four-stroke and two-stroke diesel engines have passages cast in the head to carry oil for lubrication and water for cooling.
► Direct and indirect fuel injection systems are two basic designs of fuel delivery control.
► Fuel injected directly into the combustion chamber is called direct injection.
► Fuel injected into a separate chamber in the cylinder head is called indirect injection.
► Intake and exhaust valves are used in an engine to provide a means for fresh air to enter and exhaust gases to exit the cylinder.
► Scavenging is the removal of hot exhaust gases from the cylinder and the refilling of it with fresh air.
► The crankshaft converts the reciprocating movement of the pistons into rotating movement that transmits power through the transmission and final drive unit of the vehicle.
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► Second-generation on-board diagnostics (OBDII) started in late 1995 and became standard in 1996. All vehicles use the same generic adapter for a generic scan tool to connect to the vehicles computer.
► Since California’s emission laws of the 1960s, the standards for emissions have gotten more stringent, requiring many changes to subsequent vehicles.
► OBD systems help the technician work more efficiently and help take the guesswork out of diagnosing problems on today’s sophisticated vehicles.
► OBD systems are a great resource, using powerful on-board computers in harmony with sophisticated diagnostic equipment to pinpoint problems in vehicle systems and components.
► Both OEM and aftermarket OBDII scan tools serve to access OBD information via the data link connector (DLC).
► The Society of Automotive Engineers (SAE) has standardized the terminology of parts and systems nomenclature (J1930) and across-the-board identification of generic DTCs (J2012).
► Diagnostic trouble codes (DTCs) are usually set after the vehicle has had two drive cycles with the same malfunction.
► Codes on OBD systems are categorized as power train (P), body (B), chassis controller (C), and communications system (U).
► Freeze-frame data are the best way for a technician to determine the conditions under which a concern happens which then helps determine the cause of the DTC.
► Scan tools, a lab scope, and a digital volt-ohmmeter (DVOM) are a technician’s best tools when it comes to troubleshooting an OBD code.
► Always refer to the manufacturer’s service information and follow the diagnostic flowcharts to ensure that the vehicle malfunction is identified and repaired correctly.
► Always use wiring diagrams when diagnosing any electric/electronic circuits in the OBD system, and do not forget about the grounds.
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► Modern vehicles are more sophisticated with longer maintenance intervals than early vehicles.
► Karl Benz is considered the inventor of the modern automobile (in 1885).
► Application of interchangeability and the assembly line made cars more affordable for the masses.
► Today’s production lines are high-volume, high-technology plants.
► Lube technicians carry out standard maintenance services.
► Light line technicians are responsible for maintenance and repair of mechanical and electrical components.
► Heavy line technicians diagnose and repair major engine or transmission problems and perform differential overhaul.
► Chassis and brake technicians repair the vehicle’s chassis and brakes (respectively, or in combination), including steering and suspension.
► Electrical technicians diagnose and repair the vehicle’s electrical wiring and computer-based equipment.
► Drivability technicians are responsible for inspecting the mechanical and electrical faults that can affect the performance and emissions of vehicles.
► Transmission specialists diagnose and repair transmission units (manual and automatic).
► The shop foreman is responsible for administrative duties, supervising technicians, and ensuring customer satisfaction.
► Service consultants work to ensure that customers are satisfied with their experience at the shop.
► Service managers run the service department and must create a positive work environment.
► Types of repair facilities are dealerships, independent shops, specialty shops, franchises/retailers, and fleet shops.
► Automotive technicians may become ASE certified; training programs may be NATEF accredited; school programs may be AYES authorized; and technicians may choose to receive certification in emission failures and/or air-conditioning systems.
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► In automotive applications, most emissions are the by-product of combustion and are emitted from the exhaust system.
► Not all emissions from combustion are considered hazardous.
► The term “emission”, when used in automotive circles, normally refers to the pollution produced by a light vehicle during operation or while sitting stationary.
► The fuel tank allows liquid fuel to evaporate into a gas; if not controlled, those vapors can escape into the atmosphere and are called evaporative emissions.
► In a compression-ignition diesel engine, emissions are created in the combustion chamber the same way as in spark ignition engines and escape to the atmosphere through the exhaust and the crankcase breather.
► Manufacturers are required by law and the Environmental Protection Agency (EPA) to control the emissions produced by their vehicles.
► The federal test procedure (FTP) requires all manufacturers to pass a federal emission test before vehicles can be sold in the United States.
► Not only must the vehicles pass the test before they can be sold, but also they must be capable of detecting an emission failure over the life of the vehicle, as they are being operated.
► As of 1996, all new vehicles most meet the OBDII standard, meaning all vehicles must have the same self-diagnostic connectors.
► The EPA requires that when a vehicle’s emissions deviate from the FTP limit by 1.5 times, the warning light (malfunction indicator lamp) must turn on and one or more specific diagnostic trouble codes (DTC) set in memory.
► The OBDII system was developed purely with the intent of keeping vehicles emission compliant and warning drivers if they aren’t.
► Regulated air pollutants can be divided into two groups: gases and particulates.
► Many countries follow an international protocol on emissions requiring vehicle manufacturers to comply with these laws.
► Historically, the regulated emissions have been hydrocarbons, carbon monoxide, oxides of nitrogen, and particulate matter. In recent years, carbon dioxide has been added to the list of emissions that are being regulated.
► There are three categories of emission gasses: non-harmful, harmful, and debatable.
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► Poorly maintained wheels and tires decrease effective handling and may lead to steering and suspension problems.
► The main principles of understanding service of tires and wheels are: tire distortion, center of gravity, and wheel offset.
► Tire distortion refers to the tire’s cornering force countering the side force that occurs when a vehicle corners, to create a slip angle.
► Center of gravity refers to the balance point of the vehicle, which is determined by location of the engine and transmission.
► Wheel offset refers to the distance from the hub mounting surface to the centerline of the wheel.
► Wheel offset can be zero, positive, or negative.
► Tire and wheel assemblies must be balanced to prevent both static and dynamic imbalance.
► Tire and wheel components include the wheel or rim, wheel studs and nuts, wheel center, and tires.
► Rims usually have a deep well—a widened area on one side of the wheel.
► The design of passenger vehicle wheels is generally either well based or drop center.
► Types of rims include: steel, one-piece alloy, two-piece alloy, multipiece alloy, custom, spinning, split, semi-drop well, drop well, and safety.
► Wheel studs and lug nuts fasten the wheels to the rims.
► Wheel retaining studs or nuts can be tapered seat, flat seat with washer, or flat seat without a washer.
► Tires provide the wheel with coverage and protection and absorb shock from road surfaces.
► Tires are composed of treads, sidewalls, inner liners, and beads.
► Synthetic fabric cords are used to create plies, giving the tire strength and flexibility.
► Tires are most commonly either cross-ply or radial (used by most passenger vehicles).
Source: http://www.cdxauto.com/cw/fundamentals/docs/
Web site to visit: http://www.cdxauto.com
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