The fuel is injected pulsed into the intake manifold, located directly in front of the engine intake valves, via electrically controlled injectors. The engine control unit sequentially controls the injectors in accordance with the ignition sequence, regulates the injection time and thus the amount of fuel injected.
The air required to form the fuel mixture is sucked into the engine through the air filter and passes through the throttle valve and the intake manifold to the intake valves. The amount of air sucked in is regulated by the throttle valve, which is moved by a stepper motor controlled by the engine control unit. In compressor engines, the sucked air is compressed by a compressor driven by a V-belt transmission. The compressed air is then cooled in the charge air cooler and fed to the engine to form the fuel mixture.
The volume of air sucked in is determined by the air volume meter. The meter is located in the air intake duct. The meter housing contains a thin, electrically heated sensor plate, cooled by the flow of sucked air. The electric current that heats the plate is regulated by the control system in such a way as to maintain the temperature of the plate constant. If, for example, the amount of air sucked in increases, the temperature of the heated plate begins to decrease. At the same time, the magnitude of the electric current immediately increases in order to maintain the temperature of the plate unchanged. Fluctuations in the electric current of the plate indicate to the engine control unit its load state, which allows the amount of fuel injected to be correctly determined.
The engine control unit is located in the electronics box, on the left, near the brake fluid reservoir or directly on the engine. The control unit determines the optimal ignition time, injection moment and the amount of fuel injected. At the same time, the operation of the control unit is coordinated with other systems of the car, for example, with the gearbox control or anti-theft system.
Information from other sensors and control voltages supplied to the actuators ensure optimal engine operation in any situation. If some sensors fail, the control unit switches to the emergency program mode to prevent possible engine damage and ensure further movement of the vehicle. In this case, the engine runs unevenly and tends to stall when the gas is increased.
Sensors and actuators of the injection system
Location of engine management system components using models 163.154/172/174 as an example
1 - Fuse and relay mounting block; 2 - Starter relay; 3 - Fuel pump relay; 4 - Relay circuit 15; 5 - Secondary air mixing pump relay (american models only); 6 - ECM (ME-SFI); 7 - Diagnostic connector DLC; 8 - Clutch pedal switch sensor (models with manual transmission)
Location of engine management system components using models 163.154/172/174 as an example
1 - Carbon adsorber purge control valve; 2 - Pedal position sensor; 3 - Carbon adsorber shut-off valve (american models only); 4 - Carbon adsorber; 5 - Fuel tank pressure sensor (american models only)
Location of engine management system components using models 163.154/172/174 as an example
1 - Right pre-catalytic lambda probe; 2 - Right post-catalytic lambda probe; 3 - Malfunction Indicator Lamp MIL - Except US Models; 4 - Malfunction Indicator Lamp MIL - US Models; 5 - Left post-catalytic lambda probe; 6 - Left pre-catalytic lambda probe
Location of engine management system components using models 163.154 as an example
1 - Thermo-anemometric air flow sensor MAF; 2 - Ignition coil of the third cylinder; 3 - Ignition coil of the second cylinder; 4 - Ignition coil of the first cylinder; 5 - Fuel injectors; 6 - Camshaft Hall Sensor; 7 - Coolant Temperature Sensor (ECT); 8 - Ignition coil of the sixth cylinder; 9 - Ignition coil of the fifth cylinder; 10 - Ignition coil of the fourth cylinder; 11 - Air pump relay (american models only); 12 - Air pump switch valve (american models only); 13 - Pressure sensor (american models only); 14 - Crankshaft Position Sensor (CKP)
Location of engine management system components using models 163.154 as an example
1 - Right knock sensor (KS 1); 2 - Left knock sensor (KS 2); 3 - EA/CC/ISC actuator; 4 - EGR vacuum transducer; 5 - Oil level/quality sensor; 6 - Intake manifold resonant valve-switch
The location of individual elements of the engine management system using individual models as an example is shown in the illustrations.
Crankshaft Position Sensor (CKP) screwed into the cylinder block near the flywheel. It transmits information to the control unit about the engine speed and the TDC position of the piston of the first cylinder.
Camshaft Position (CMP) Sensor is located at the end of the cylinder head cover. Together with the crankshaft position sensor, it transmits information about the TDC of the piston of the first cylinder to the control unit. It serves to synchronize the ignition timing and ignition sequence.
Throttle actuation mechanism consists of an electric motor and two potentiometers. The mechanism regulates the position of the throttle valve, ensuring stability of idle speed, regardless of the connection of additional energy consumers, such as a power steering or air conditioning compressor.
Throttle Position Sensor (TPS) is mounted in the actuator of the throttle valve and provides the control unit (ECM) with information about the current angle of the throttle valve position. The second potentiometer informs the ECM about the base value and generates a backup signal if the throttle valve potentiometer fails.
Accelerator pedal position sensor is located in the area of the driver's feet directly on the axis of the gas pedal. It informs the control unit about the position of the pedal. For safety reasons, an additional signal is taken from the pedal sensor, as well as from the throttle potentiometer.
[Information copied from the website: Mercedesman.ru]
Coolant Temperature (ECT) Sensor is located in the thermostat housing. It is a resistor with a negative temperature coefficient (NTC), the resistance of which decreases with increasing temperature.
Intake Air Temperature (IAT) Sensor also represents an NTC resistor.
Fuel Tank Ventilation/Evaporative Emissions (EVAP) System consists of a carbon adsorber and an electromagnetic valve for controlling the purge of the latter. The adsorber accumulates fuel vapors formed as a result of its heating. When the engine is running, the fuel vapors accumulated in the adsorber are drawn into the intake tract and sent to the combustion chambers.
Lambda probes (oxygen sensors) measure the oxygen content in the exhaust gases before and after the catalytic converter and transmit the corresponding signals to the engine control unit. One lambda probe is located before and the other after the catalytic converter.
Knock sensor(s) (KS) it is screwed directly into the cylinder block body and serves to prevent the occurrence of dangerous shock combustion of the fuel mixture, allowing the ignition timing to be maintained at the detonation limit, when the engine efficiency is maintained at the maximum level with minimum fuel consumption.