Mercedes M-Class W163

since 1997 release

Repair and operation of the car

Principle of functioning of a control system and injection of the petrol engine

Fuel is sucked in from the fuel tank by the electric fuel pump and moves via the fuel filter to the fuel distributive highway. The regulator of pressure provides maintenance of pressure in fuel system in the range of 3.2 ÷ of 3.6 atm.

Through the electrooperated injectors fuel pulsewise is injected into the inlet pipeline located just before inlet valves of the engine. The control unit of the engine makes consecutive management of injectors according to an ignition order, regulates injection time and by that amount of injectable fuel.

The air necessary for formation of fuel mix is sucked in by the engine via the air filter and arrives through a butterfly valve and the inlet pipeline to inlet valves. The amount of the soaked-up air is regulated by a butterfly valve which moves the step electric motor operated by the engine control unit. At compressor engines the soaked-up air compresses the compressor set in motion from klinoremenny transfer. Then compressed air is cooled in a cooler of the forced air and comes to the engine for formation of fuel mix.

The volume of the soaked-up air is defined by the measuring instrument of amount of air. The measuring instrument is located in kanalevsasyvayemy air. In the case of the measuring instrument the thin, electrically warmed touch plate cooled by the passing stream of the soaked-up air is located. The electric current heating a plate is regulated by a control system so that to maintain constant plate temperature. If, for example, the amount of the soaked-up air increases, temperature of the heated plate begins to decrease. At the same time the size of electric current at once increases to keep temperature of a plate invariable. Fluctuations of electric current of a plate indicate to the control unit of the engine its state loadings that allows to define amount of injectable fuel correctly.

The control unit of the engine is in electronics box, at the left, about the tank of brake fluid or directly on the engine. The control unit defines optimum time of ignition, the moment of injection and amount of injectable fuel. At the same time there is a coordination of operation of the control unit with other systems of the car, for example, to control of the transmission or anticreeping system.

Information from other sensors and the operating tension arriving to executive bodies ensures optimum functioning of the engine in any situation. If some sensors fail, the control unit switches in the mode of the emergency program to exclude possible damage of the engine and to provide the further movement of the car. In this case the engine works unevenly and at increase in gas has tendency to a stop.

Sensors and executive bodies of system of injection

Arrangement of components of a control system of the engine on the example of models 163.154/172/174

1 — the Assembly block of safety locks and the relay 2 — the starter Relay 3 — the Relay of the fuel pump 4 — the Relay of a contour 15	5 — the Relay of the pump of admixture of secondary air (only American models) 6 — ECM (ME-SFI) 7 — the Diagnostic DLC socket 8 — the coupling pedal Sensor switch (models with RKPP)

Arrangement of components of a control system of the engine on the example of models 163.154/172/174

Arrangement of components of a control system of the engine on the example of models 163.154/172/174

Arrangement of components of a control system of the engine on the example of models 163.154

Arrangement of components of a control system of the engine on the example of models 163.154

Location of separate elements of a control system of the engine on the example of separate models is shown on illustrations.

The sensor of provision of a bent shaft (CKP) is screwed in the block of cylinders at a flywheel. He transfers to the control unit information on the speed of the engine and the provision of VMT of the piston of the first cylinder.

The sensor of position of the camshaft (CMP) is located in an end face of a cover of a head of cylinders. He together with the sensor of provision of a bent shaft transfers to the control unit information on VMT of the piston of the first cylinder. It serves for synchronization of the moment of ignition and the sequence of ignition.

The executive mechanism of a butterfly valve consists of the electric motor and two potentiometers. The mechanism regulates the provision of a butterfly valve, providing stability of turns of idling, is not dependent on connection of additional consumers of energy, such as steering amplifier or К/В compressor.

The sensor of provision of a butterfly valve (TPS) is built in in the executive mechanism of a butterfly valve and issues information on the current coal of provision of a butterfly valve on the control unit (ECM). The second potentiometer reports to ECM data on basic value and forms a spare signal at failure of a potentiometer of a butterfly valve.

The sensor of position of the accelerator pedal is located the region of an arrangement of legs of the driver directly on an accelerator pedal axis. He gives the control unit information on the provision of a pedal. For safety reasons from the sensor of a pedal the additional signal, just as from a potentiometer of a butterfly valve undertakes.

The sensor of temperature of cooling liquid (ECT) is located in the thermostat case. It represents the resistor with negative temperature coefficient (NTC) which resistance decreases with growth of temperature.

The sensor of temperature of the soaked-up air (IAT) also represents the NTC resistor.

The system of ventilation of a fuel tank / catching of fuel evaporations (EVAP) consists of a coal adsorber and the electromagnetic valve of management of a purge of the last. In an adsorber the fuel vapors which are formed as a result of its heating accumulate. During the operation of the engine the fuel evaporations which accumulated in an adsorber are extended to the inlet highway and go to combustion chambers.

Lambda probes (oxygen sensors) measure the content of oxygen in the fulfilled gases before and after the catalytic converter and transmit the corresponding signals to the control unit of the engine. One lambda probe another is located before, and after the catalytic converter.

The sensor(s) of a detonation (KS) is rolled directly in a body of the block of cylinders and serves for prevention of emergence of dangerous shock combustion of fuel mix, allowing to hold installation of the moment of ignition on detonation border when efficiency of return of the engine is maintained at the maximum level at the minimum fuel consumption.