Unit Two PDF: Vehicle Maintenance and Servicing

Unit Two: Remove and disassembled system assemblies Unit Two: Service and maintenance schedules and job order A, Vehicle Maintenance and Servicing Vehicle maintenance and servicing is carried out when the vehicle completes certain kilometers on its normal running or when the v...

Unit Two: Remove and disassembled system assemblies Unit Two: Service and maintenance schedules and job order A, Vehicle Maintenance and Servicing Vehicle maintenance and servicing is carried out when the vehicle completes certain kilometers on its normal running or when the vehicle does not give proper performance. It is suggested that the vehicle owners carry out regular and periodical checks on their vehicle  B, Daily Inspection (DI) It is the responsibility of a driver or owner of a vehicle to carry out the following inspection and checks daily, before starting the engine, to avoid any type of breakdown on the road.  Check tire pressure in all the tires visually or by hitting the tire wall with the help of a stone and judge the sound Check the radiator’s coolant level Check the fan belts for looseness Check the level of engine oil Check the windscreen, rear-view mirror and rear window glass for their cleanliness  C. Maintenance Check-up When one plans a long-distance travel, it is necessary to carry out a routine check-up. One should read the vehicle maintenance manual for clarity. Some important check-ups are done for better maintenance Topping of oil level Proper tension of belt Battery for cleanliness and level of electrolyte Brakes Air conditioning Topping up of coolant, if required, in the coolant reservoir  Checking the serviceability of cooling system hoses Proper tire inflation pressure  1.2 Overview of service techniques Visual check  A visual inspection report form is completed by quality assurance inspectors to document pass/fail decisions on visually inspected products based on set defect criteria.  Use this checklist to effectively indicate product ID and location, capture photo evidence of products and/or defects, determine pass/fail decisions based on a reference image, identify visual defects based on defect criteria, and complete the visual inspection with a digital signature Sound/aural checks  Diagnosing engine noise is often one of the most difficult tasks you can deal with. Most of the noises that come from the engine can be described by such words as:  Piston Ring Noise Sounds like: Clicking noise during acceleration. Common causes: Low ring tension, broken rings, or worn cylinder walls  Piston Slap Sounds like: Continuous muffled, hollow sound. Common causes: Excessive piston-to-wall clearance, worn cylinders or inadequate oil.  Crankshaft Knock Sounds like: Dull, heavy, metallic knock under load. Common causes: Worn bearings; main, rod, or thrust.  Valve train Noise Sounds like: Regular clicking noise at half-speed. Common causes: Excessive valve clearance or defective valve lifter.  Detonation Sounds like: High-pitched metallic pinging noise. Common causes: Improper timing, lean air/fuel ratio, or improper octane.  1.3 Adjustment of system/components Valve Adjustment  To check the clearance of any valve accurately, hot or cold, you must rotate the engine so that the valve is fully closed and the heel, or base circle, of the came lobe is on the tappet.  This provides maximum clearance. Insert a flat feeler gauge of the specified thickness between the valve stem and the rocker arm or cam follower.  In overhead valve layouts it’s rather more difficult because the camshaft cannot be seen with these or any or similar layout there is some method of setting the gap at its widest.  Valve identification  The location of the valve in relationship to the manifold braches at the cylinder head.  Example if the exhaust manifold branches terminate at the end of the cylinder head, then the first & the last valves are both exhaust. The valve layout of a typical four cylinder engine would be E,I,I E,E,I,I,E. Where E =Exhaust &I= Intake. A further method of identifying which valve is which is to turn the engine over in its normal direction of rotation and watch the valves (or rockers), at each cylinder, the exhaust valve will open &close, will be immediately followed by the inlet.  Disassembling engine exterior assembly Detach the injection pump and high-pressure lines. The air compressor should be removed. If the engine have oil cooler, remove the oil cooler. Remove oil and fuel filters. Remove the alternators and its driving belts. Remove the starter motor and its wire harness Remove steering gear fluid pump. Detach the water pump from its mounting part. Remove the intake manifold and exhaust manifold with the turbo charger. Remove all injectors and glow plugs Engine temperature and oil pressure senior should be removed A) Removing and Disassemble engine systems Cooling system  The cooling system keeps the engine at its most efficient temperature at all speeds and operating conditions.  In addition, the cooling system provides a source of heat for the passenger compartment heater Types of cooling systems a) Air-cooled/ direct b) Liquid-cooled/in direct A) Removing and Disassemble engine systems 12 13  The cooling system keeps the engine at its most efficient temperature at all speeds and operating conditions. Burning fuel in the engine produces heat. Some of this heat must be taken away before it damages engine parts. This is one of the three jobs performed by the cooling system. It also helps bring the engine to normal operating temperature as quickly as possible. In addition, the cooling system provides a source of heat for the passenger compartment heater. There are two types of cooling systems found on cars: 1 liquid-cooling system(indirect) and 2 air –cooling system(direct) 14 1 Air Cooling Some older cars, are air-cooled. Instead of circulating fluid through the engine, the engine block is covered in aluminum fins that conduct the heat away from the cylinder. A powerful fan forces air over these fins, which cools the engine by transferring the heat to the air. 15 Air Cooling 16 2 Liquid Cooling The cooling system on liquid-cooled cars circulates a fluid through pipes and passage ways in the engine. As this liquid passes through the hot engine it absorbs heat, cooling the engine. After the fluid leaves the engine, it passes through a heat exchanger, or radiator, which transfers the heat from the fluid to the air blowing through the exchanger. 17 Liquid Cooling 18  LIQUID Cooling-System Components and their Functions 1 Radiator – heat exchanger that removes heat from coolant passing through it; receives hot coolant from the engine and returns the coolant to the engine at a lower temperature. Radiators are normally based on one of two designs: cross flow or down flow. 19 20 2 Water Pump The heart of the cooling system is the water pump. Its job is to move the coolant through the system. Typically the water pump is driven by the crankshaft through pulleys and a drive belt 21 22 23 3 Radiator Pressure Cap  Seals the radiator  Pressurizes the system  Relieves excess pressure  Allows coolant flow between the radiator and the coolant reservoir 24 3.1 Radiator Cap Pressure Relif Valve  Spring-loaded disk  Normally, water boils at 212ºF (100ºC)  Typical pressure: raises the boiling point to 250–260ºF (121–127ºC) 25 3.2 Radiator Cap Vacuum Valve Opens to allow flow back into the radiator when the coolant temperature drops 26  4 Expansion Tank  Cooling systems with expansion tanks are called closed-cooling systems. They are designed to catch and hold any coolant that passes through the pressure cap. As the engine warms up, the coolant expands. This eventually causes the pressure cap to release. The coolant passes to an expansion tank. When the engine is shut down, the coolant begins to shrink. Eventually, the vacuum spring inside the pressure cap opens and the coolant in the expansion tank is drawn back into the cooling system. 27 28 5 , Hose Upper and lower hoses Coolant flows from the engine to the radiator and from the radiator to the engine through radiator hoses. 29 30 6 Water Jackets Hollow passages in the block and cylinder heads surround the areas closest to the cylinders and combustion chambers. 31  7 Hose clamp Hoses are attached to the engine and radiator with clamps. Hose clamps are designed to apply clamping pressure around the outside of the hose at the point where it connects to the inlet and outlet connections at the radiator, engine block, water pump, or heater core. 32  8 , Belt Drives Belt drives are used to power the water pump and/or cooling fan on many engines. The belts must be in good condition and properly tensioned in order to drive this at the correct speed. 33  9, Cooling Fans The efficiency of the cooling system depends on the amount of heat that can be removed from the system and transferred to the air. At highway speeds, the ram air through the radiator should be sufficient to maintain proper cooling. At low speeds and idle, the system needs additional air. This air is delivered by a fan 34 35  9.1 Electric Cooling Fans In most late-model applications, to save power and reduce the noise level, the conventional belt-driven, water pump– mounted engine cooling fan has been replaced with an electrically driven fan. This fan and motor are mounted to a shroud. The 12-volt, motor-driven fan is electrically controlled by an engine coolant temperature switch and/or the air conditioner switch. 36 37  10 Thermostat  Senses the coolant temperature and controls coolant flow through the radiator  Reduces coolant flow in a cold engine  Increases coolant flow in a hot engine Thermostat Operation A. Cold engine B. Hot engine 38  11 Temperature Indicators Coolant temperature indicators alert the driver of an overheating condition. These indicators are a temperature gauge and/or a warning light. A temperature sensor is threaded into a bore in a water jacket 39  12 ,Coolant Engine coolant is a mixture of water and antifreeze. Engine coolant has a higher boiling temperature and a lower freezing point than water. The exact boiling or freezing temperatures depend on the mixture. The typical recommended mixture is a 50/50 solution of water and antifreeze/coolant. 40 Antifreeze/Water Mixture Lowers the coolant freezing point to about –34 ºF (–37 ºC) 41  B) Cooling system problem a) Engine overheating Condition Cause Overheats any time or Low coolant level Overheats in heavy Low coolant level traffic or after idling Erratically Faulty radiator cap fora long time Faulty radiator cap Faulty thermostat Faulty thermostat Temperature sender or related electrical problem Cooling fan is not turning on Cooling fan is not turning on Restricted airflow through the radiator Overheats shortly Temperature sender or related electrical problem Leaking head gasket after the engine is started Restricted exhaust Seems slightly too hot Radiator and/or block are internally clogged with rust, scale, silt, or gel Water pump impeller is corroded all of the time; gauge Overheats when Radiator and/or block are internally clogged with Restricted airflow through the radiator nears the red zone at rust, scale, silt, or gel Faulty radiator cap driving at speed, or times after repeated Restricted airflow through the radiator Faulty thermostat heavy Faulty radiator cap Radiator fins are corroded and falling off acceleration Collapsed lower radiator hose Faulty thermostat Radiator fins are corroded and falling Cooling fan is not turning on off  Bubbles in the coolant Faulty radiator cap expansion tank Failed head gasket Air in the radiator but the Coolant leak expansion tank is full Faulty radiator cap Air in the system Faulty seal between the radiator cap and expansion tank Failed head gasket  b) Check for external leaks i. External leaks  Cracked cylinder block  Faulty radiator cap  Dented radiator inlet of outlet tube  Radiator leak  Cracked or porous water pump housing  Water core leak  Loose core hole plug in cylinder block  Cracked thermostat housing  C) Cooling system inspection and test A ) Inspecting Cooling System for Leaks B) Temperature Test C) Radiator Checks D) Checking Hoses E) Checking Fans and Fan Clutches F ) Thermostat Lubrication system Properties of Lubricating Oil 1. Minimize Friction Prevent Wear 2. Act as a coolant 3. Act as a Hydraulic Medium 4. Prevent Corrosion. 5. Prevent formation of deposits 6. Carry away contaminants  Properties of Lubricating Oil 1.Proper Viscosity 2.Viscosity Index – this is a measure of how much the viscosity of an oil changes with temperature. 3.Viscosity Numbers – lubricating oils either in single or multi-viscosity oils are rated according to its numbers. SAE 30 or SAE 40 are examples of a single-viscosity oil and SAE20W50 is also an example of a multi-viscosity oil. The letter W indicated in multi-viscosity oil stands for Winter Grade and the word SAE means Society of Automotive Engineers. 4.Resistance to Carbon Formation and Oil Oxidation. 5.Corrosion and rust Inhibitors – 6.Foaming Resistance – the churning action of the crankshaft causes the oil to foam or aerate thus reduces the lubricating effectiveness of the oil. As a result, an additive is mix to prevent the oil to foam. 7.Detergent-Dispersant – 8.Extreme-pressure Resistance – 9.Energy-Conserving Oil – this is a property of an oil which reduces fuel consumption when compared to engine operation. 10.Synthetic Oil – these oils are made by chemical processes and do not necessarily come from petroleum. This is a property of an oil which tolerates heat better than other oils while producing less sludge and carbon deposits  Types of Lubricating System 1. Splash Type – it refers to the system in which the oil is being splashed from the oil pan into the lower part of the crankcase. Usually, the connecting rod has a dipper that dips into the crankcase oil each time the piston reaches BDC. Likewise, usually used in a smaller like a single cylinder engine. 2. Pressure Feed Type – this type of lubricating system connotes that the engine parts are lubricated by oil fed under pressure from the oil pump.  Component Parts of the Lubricating System 1) Crankcase / oil pan – it is an iron or aluminum casting enclosing the crankshaft; it is usually considered as the storage of oil in the engine. 2) Oil Pump – it refers to a pump, which circulates lubricating oil from the engine’s sump through the lubrication system. Likewise, an oil pump has of three kinds, to wit: A) Rotary pump B) The gear pump C) The crescent pump 3. Oil Pickup and Strainer  The oil pickup is a tube that extends from the oil pump to the bottom of the oil pan.  The strainer has a mesh screen suitable for straining large particles from the oil and yet passes a sufficient quantity of oil to the inlet side of the oil pump. 4. Oil Filter  The oil filter removes most of the impurities that have been picked up by the oil, as it circulates through the engine.  Designed to be replaced readily, the filter is mounted in an accessible location outside the engine 5. Oil Galleries  Oil galleries are small passages through the cylinder block and head for lubricating oil. They are cast or machined passages that allow oil to flow to the engine bearing and other moving parts  The main oil galleries are large passages through the center of the block. They feed oil to the crankshaft bearings, camshaft bearings, and lifters.  The main oil galleries also feed oil to smaller passage running up to the cylinder heads. 6. Oil Pressure Warning Light  The oil pressure warning light is used in place of a gauge on many vehicles. The warning light, although not as accurate, is valuable because of its high visibility in the event of a low oil pressure condition.  Because the engine can fail or be damaged in less than a minute of operation without oil pressure, the warning light is used as a backup for a gauge to attract instant attention to a malfunction 7. Oil cooler  Oil cooler is a heat exchanger which is either air cooled type or liquid cooled type.  In air-cooled oil cooler, oil flow through heat exchanger tubes and coolant (air) passing over the tubes where as in liquid cooled cooler, both oil and coolant (water), the two being separated by tubes or baffles, flow through heat exchanger  Lubricating system problem diagnosis The four problems most often occur in the lubrication system are as follows: 1. High oil consumption (oil must be added frequently) 2. Low oil pressure (gauge reads low, indicator light glows, or abnormal engine noises) 3. High oil pressure (gauge reads high, oil filter swelled) 4. Defective indicator or gauge circuit (inaccurate operation or readings) 1. High oil consumption (oil must be added frequently) External oil leakage out of the engine or internal leakage of oil into the combustion chambers causes high oil consumption. A description of each of these problems is as follows:  External oil leakage—detected as darkened oil wet areas on or around the engine. Oil may also be found in small puddles under the vehicle. Leaking gaskets or seals are usually the source of external engine oil leakage.  Internal oil leakage—shows up as blue smoke exiting the exhaust system of the vehicle. For example, if the engine piston rings and cylinders are badly worn, oil can enter the combustion chambers and will be burned during combustion 2. Low oil pressure (gauge reads low, indicator light glows, or abnormal engine noises) Low oil pressure is indicated when the oil indicator light glows, oil gauge reads low, or when the engine lifters or bearings rattle. The most common causes of low oil pressure are as follows: 1. Low oil level (oil not high enough in pan to cover oil pickup) 2. Worn connecting rod or main bearings (pump cannot provide enough oil volume) 3. Thin or diluted oil (low viscosity or fuel in the oil) 4. Weak or broken pressure relief valve spring (valve opening too easily) 5. Cracked or loose pump pickup tube (air being pulled into the oil pump) 6. Worn oil pump (excess clearance between rotor or gears and housing) 7. Clogged oil pickup screen (reduce amount of oil entering pump) A low oil level is a common cause of low oil pressure. Always check the oil level first when troubleshooting a low oil pressure problem.  3. High oil pressure (gauge reads high, oil filter swelled) High oil pressure is seldom a problem. When it occurs, the oil pressure gauge will read high. The most frequent causes of high oil pressure are as follows: 1.Pressure relief valve struck (not opening at specified pressure) 2.High relief valve spring tension (strong spring or spring has been improperly shimmed) 3.High oil viscosity (excessively thick oil or use of oil additive that increases viscosity) 4.Restricted oil gallery (defective block casting or debris in oil passage)  4. Defective indicator or gauge circuit (inaccurate operation or readings) The indicator light may stay on or flash, pointing to a low oil pressure problem. The gauge may read low or high, also indicating a lubrication system problem.  Inspect the indicator or gauge circuit for problems.  The wire going to the sending unit may have fallen off.  The sending unit wire may also be shorted to ground (light stays on or gauge always reads high).  To check the action of the indicator or gauge, remove the wire from the sending unit.  Exhaust Gas System  When the combustion ends in each cylinder, the exhaust gas must be collected, cleaned, quieted, and then discharged into the air. This is the job of the exhaust system.  This system includes the exhaust manifold, exhaust pipe, catalytic converter, muffler or silencer, resonator (on some cars), and tail pipe.  Exhaust system component a) Exhaust Manifold  The exhaust manifold is made of cast iron and is bolted over the exhaust ports of the engine.  It collects exhaust gas from different cylinders. B ) Exhaust Pipe The exhaust pipe is a long pipe leading from the exhaust manifold to the muffler. C) Catalytic converter  Catalytic converters provide another way to treat the exhaust gas.  These devices located in the exhaust system, convert harmful gases into harmless gases.  Inside the catalytic converter, the exhaust gases Passover a catalyst. D ) Muffler The exhaust gas emerges in a pulsating flow and therefore causes marked vibration in the exhaust pipes and mufflers (silencers). E) Resonator It is used to further muffle the noise of the exhaust gases. It is also called secondary muffler. F) Tail Pipe The tail pipe is a pipe that carries the exhaust gases from the muffler to the rear of the vehicle.  Fuel system Automobile engines mostly use two types of fuels gasoline and diesel fuel. These fuels must reach to the engine cylinders and be ignited. Three basic types of fuel systems are used in automobile engines 1. Gasoline fuel systems (carburetor and gasoline fuel injection) 2. Diesel fuel system 3. Alternative fuel system  1. Gasoline fuel system The carbureted fuel system consists of the fuel tank, fuel pump, fuel filter, carburetor, intake manifold, and fuel lines. The fuel lines are tubes connecting the tank, fuel pump, and carburetor. Most of these components are the same in both the carbureted and the fuel-injection systems. Each component is described in following sections  Fuel tank  The fuel tank is a reservoir that holds the fuel supply and helps maintain its temperature at a level below its flash point. The fuel supply pump, often referred to as the lift pump, is responsible for drawing fuel from the tank and delivering it to the high pressure pump. Modern day fuel pumps can be electrically or mechanically driven by the engine.  Fuel Lines A fuel line is a hose or pipe used to transfer fuel from one point in a vehicle to another. Materials like Rubber , Plastic , Steel... Lines are placed away from exhaust pipes, mufflers, and manifolds, so that excessive heat will not cause vapor lock.  FUEL PUMPS  The fuel pump is used to lift fuel from the tank and supplies the it to the carburetor. This is because the fuel tank is placed lower than the carburetor, the fuel does not flow naturally to the carburetor. Two types of fuel pumps are used: 1.The mechanical type (delivery pressure 0.2-0.3 bar) 2. The electric type (delivery pressure 2 - 4.7 bar). Location In-Tank Type In-Line Type  Fuel Filters The fuel filter is the key to a properly functioning fuel delivery system. This is more true with fuel injection than with carbureted cars. Fuel injectors are more susceptible to damage from dirt because of their close tolerances, but also fuel injected cars use electric fuel pumps. When the filter clogs/blocks, the electric fuel pump works so hard to push past the filter, that it burns itself up. Fuel charcoal canister The main purpose of the charcoal filter and the charcoal canister is to absorb excess gas fumes from the fuel system and the go to gas tank while the engine is off. The filter inside of the canister acts like a sponge and absorbs all of the excess gas fumes. Once the engine is restarted, the excess gas vapors return to the fuel system and into the combustion chamber. Over time, excess buildup can clog up the charcoal canister and prevent the gas fumes from entering or exiting the canister.  Carburetor terminologies A. Carburetion  Carburetion is the mixing of the gasoline fuel with air to get a combustible mixture. The function of the carburetor is to supply a combustible mixture of varying degrees of richness to suit engine operating connections B. Vaporization  When a liquid changes to a vapor, it is said to evaporate. C. Atomization  To produce very quick vaporization of the liquid gasoline, it is sprayed into the air passing through the carburetor. Spraying the liquid turns into many fine droplets. This effect is called atomization because the liquid is broken up into small droplets (but not actually into atoms, as the name implies). D. Venturi Effect  The pistons move down on the intake strokes, a partial vacuum is produced in the cylinders. A partial vacuum is any pressure less than atmospheric pressure. Atmospheric pressure pushes air, or air-fuel mixture, into the cylinders to fill the vacuum. As the air flows toward the engine cylinders, it must first pass through the carburetor. E. Air-fuel-ratio requirements Continue…  The fuel system must vary the air-fuel ratio to suit different operating requirements. The mixture must be rich (have a high proportion of fuel) for starting. It must be leaner (have a lower proportion of fuel for part-throttle medium-speed operation.  For example , a rich mixture of about 9:1 '(9 pounds [4 kg] of air for each pound [0.45 kg] of fuel) is supplied for starting. Then, during idle, the mixture leans out to about 12:1. At medium speeds, the mixture further leans out to about 15:1 or leaner. Some engines run on mixtures as lean as 20:1. But at higher speeds, with a wide-open throttle, the mixture is enriched to about 13:1. F. Throttle Valve action  The throttle valve is a round disk below the venturi and fuel nozzle in the carburetor.  The air horn is the round cylinder through which air flows on its way to the engine cylinders.  The air picks up a change of fuel vapor while passing through the venturi. The throttle valve can be tilted more or less to allow more or less air-fuel mixture to flow through. More air flowing through the venturi increases the venturi vacuum. This causes more fuel to flow from the nozzle.  Carburetor The process of preparing combustible air fuel mixture in the petrol engine is called carburetion. A device which does this process is called carburetor. The carburetor atomizes the fuel and mixes it with air in correct proportions according to the engine operating conditions. Requirements of Carburetors The spark ignition engines fitted to automotive vehicles have to operate under variable speed and load conditions. The requirements of a good carburetor as follows:  Easy engine starting, particularly under low ambient conditions  Ability to give full power quickly after starting the engine  Smooth engine operation at various loads  Quick acceleration of the engine  Developing sufficient power at high engine speeds  Good fuel economy  Ensuring full torque at low speeds  Simple and compact in construction Carburetor Systems Carburetor Systems 1. Float System  2.Idle and Low Speed System A. Idle System B. Fast idle System 3. Main-Metering System  4. Power System  When a driver wants full power, the accelerator pedal is pushed to the floor (i.e. to the maximum position). This causes the throttle valve to open wide. Another system in the carburetor comes into action to additional fuel. This system is called power system.  5. Choke System  When a cold engine is being cranked for starting, extra fuel must be delivered to the engine. The choke valve does this job.  6. Acceleration Pump System  This condition occurs when the accelerator pedal is pushed down suddenly to increase the speed. To get the power needed, the engine has to be supplied rich mixture immediately. Electronic Fuel Injection A gasoline injection system has several possible advantages over a carburetor type of fuel system. Some advantages are as follows: * Improved atomization. Fuel is forced into the intake manifold under pressure that helps break fuel droplets into a fine mist. * Better fuel distribution. Equal flow of fuel vapors into each cylinder. * Smoother idle. Lean fuel mixture can be used without rough idle because of better fuel distribution and low- speed atomization. * Lower emissions. Lean efficient air-fuel mixture reduces exhaust pollution. * Better cold weather drivability. Injection provides better control of mixture enrichment than a carburetor. * Increased engine power. Precise metering of fuel to each cylinder and increased air flow can result in more horsepower output. * Fewer parts. Simpler, late model, electronic fuel injection system have fewer parts than modern computer-controlled carburetors. There are many types of gasoline injection systems. A basic knowledge of the different classifications : * single- or multi-point injection * indirect or direct injection Single and Multipoint EFI Systems Fuel injection systems classified by point of injection. Single Point Fuel Injection (Throttle Body Injection - TBI) Injector located inside throttle body, sits on top of inlet manifold. Air in Fuel in Injector sprays fuel Injector from above throttle valve. Throttle body ECU controls injector opening. Throttle valve Inlet manifold Single and Multipoint EFI Systems Multipoint Fuel Injection Injector located in each branch of inlet manifold, below throttle valve. Air in Injectors spray fuel Throttle valve directly into each port. Injectors x 4, x6, Fuel in x8 etc. ECU controls opening of injectors. Inlet manifold A multi-point injection system, also called port injection, has an injector in the port (air-fuel passage) going to each cylinder. Gasoline is sprayed into each intake port and toward each intake valve. Thereby, the term multipoint (more than one location) fuel injection is used. Overview of a computer-controlled high-pressure common rail V-8 diesel engine  Electronic Injectors The injectors can survive the excessive temperature and pressure of combustion by using the fuel that passes through it as a coolant  An indirect injection system sprays fuel into the engine intake manifold. Most gasoline injection systems are of this type. Direct injection forces fuel into the engine combustion chambers. Diesel injection systems are direct type. So Gasoline electronic Direct Injection System is Classified as : multi-point and Direct injection systems Fuel System Diagrams and Schematics Fuel System Block Diagrams - 1 System and subsystem Each block represents a blocks system. Lines represent connections between systems. Arrows represent direction of flow. Connection lines Direction of information flow/control Fuel System Block Diagrams - 2 System and Connection lines component Each block represents a blocks component. Lines represent connections between systems. Arrows represent direction of flow. Direction of information flow/control Electronic control unit In automotive electronics, electronic control unit (ECU) is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle. An engine control unit (ECU), also known as power-train control module (PCM), or engine control module (ECM) is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running. It does this by reading values from multidimensional maps which contain values calculated by sensor devices monitoring the engine. Working of ECU Control of fuel injection: ECU will determine the quantity of fuel to inject based on a number of parameters. If the throttle pedal is pressed further down, this will open the throttle body and allow more air to be pulled into the engine. The ECU will inject more fuel according to how much air is passing into the engine. If the engine has not warmed up yet, more fuel will be injected. Control of ignition timing : A spark ignition engine requires a spark to initiate combustion in the combustion chamber. An ECU can adjust the exact timing of the spark (called ignition timing) to provide better power and economy.  Control of idle speed : Most engine systems have idle speed control built into the ECU. The engine RPM is monitored by the crankshaft position sensor which plays a primary role in the engine timing functions for fuel injection, spark events, and valve timing. Idle speed is controlled by a programmable throttle stop or an idle air bypass control stepper motor. Common rail and Pressure sensor The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high pressure fuel.  Fuel Injection System Electronic Fuel Injection uses various engine sensors and control module to regulate the opening and closing of injector valve. Fuel delivery system Air induction system Sensor system  Fuel Delivery system Electrical Fuel Pump draws fuel from tank and forces it into the regulator. Pressure Regulator controls the amount of pressure that enters the injector and any extra fuel is returned to the fuel tank. Fuel Injector is simply a coil or solenoid operated valve. Spring pressure holds the injector closed. When engaged, the injector sprays fuel into the engine. Injector Pulse Width indicates the time each Injector is energized (Kept Open).  Sensor System Monitors engine operating condition and reports this information to ECM (computer). Sensors are electrical devices that change resistance or voltage with change in condition such as temperature, pressure and position.  Engine Sensors Oxygen Sensor measures the oxygen content in engine exhaust. Mounted on the exhaust system before the catalytic converter. Voltage out-put of O2 sensor changes with the change in oxygen content of exhaust. Lean mixture decreases the voltage. Rich mixture increases the voltage. Signal is sent to ECM and the ECM changes the time that an injector is open or close.  Engine Sensors Throttle Position Sensor (TPS) Variable resister connected to the throttle plate. Change in throttle angle = change in resistance. Based on the resistance, ECM richens or leans the mixture.  Engine Sensors Engine Temperature Sensor Monitors the operating temperature of the engine. Exposed to engine coolant. Engine cold = Low Resistance = Rich Mixture Engine Hot = High Resistance = Lean Mixture.  Engine Sensors Mass Air Flow Sensor (MAF) Measures the amount of outside air entering the engine. Contains an air flap or door that operates a variable resistor. Helps computer to determine how much fuel is needed.  Engine Sensors Inlet Air Temperature Sensor Measures the temperature of air entering the engine. Cold air (more dense) = More fuel for proper AF ratio.  Engine Sensors Crankshaft Position Sensor Detects engine speed. Changes injector timing and duration. Higher engine speed = More fuel  EFI EFI Multi port Injection System Injector is pressed into the runner(Port) in the intake manifold. Injector sprays towards an engine intake valve. Each cylinder has it’s own injector EFI Direct fuel Injection System Injectors are pressed into the combustion chamber and spray fuel directly into the combustion chamber.  2.Diesel-Engine Fuel Systems  The automotive diesel-engine fuel system uses injection nozzles or injectors similar to the fuel injectors in gasoline fuel-injection systems.  The gasoline injectors are solenoid operated. When high pressure is applied, they open and spray fuel. i. Constructions and operation  A typical fuel delivery system includes a fuel tank, fuel lines, fuel filters, and a pump.  The system works by using a pump to draw fuel from the fuel tank and passing it under pressure through fuel lines and filters to the fuel injection system.  The filter removes dirt and other harmful impurities from the fuel.  A fuel line pressure regulator maintains a constant high fuel pressure.  This pressure generates the spraying force needed to inject the fuel.  Excess fuel not required by the engine returns to the fuel tank through a fuel return line. Diesel Engine Fuel Systems