Mercedes C-Class

W203 since 2000 of release

Repair and operation of the car

Mercedes-Benz
+ Mercedes-Benz cars of class C (W-203)
+ Operation manual
+ Routine maintenance
+ Engine
+ Cooling system and heating
- Power supply system and release
   + Power supply system of the petrol and diesel engine
   - System of injection of fuel of the petrol engine
      Security measures during the work with system of injection of the petrol engine
      Functioning of a control system and injection of the petrol engine
      General check of system of injection of the petrol engine
      Removal and installation of the measuring instrument of mass of air
      Check of injectors
      Removal and installation of the fuel distributive highway and injectors
      Check and adjustment of speed of the single course / moment of ignition/concentration WITH
   + System of injection of fuel of the diesel engine. Turbocompressor
   + Systems of release and decrease in toxicity of the fulfilled gases. Turbocompressor
+ Engine electric equipment
+ Manual transmission
+ Automatic transmission
+ Coupling and power shafts
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment

Functioning of a control system and injection of the petrol engine

Arrangement of components in a motive compartment of the C240 and C320 models


1 — the Sensor of a detonation (KS) 1 (On the right on the engine) 2 — the Sensor of a detonation (KS) 2 (At the left on the engine) 3 — the Sensor of provision of a butterfly valve (TPS)	4 — the Vacuum EGR transmitter 5 — the Valve switch of a configuration of the inlet pipeline 6 — the Sensor of temperature/quality/level of oil

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, equal 3.2 – 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 the channel of the soaked-up 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

The sensor of provision of a bent shaft 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 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. It regulates the provision of a butterfly valve. Thanks to it the stable speed of idling is reached, the power steering or the compressor of the conditioner is not dependent on connection of additional consumers, such as.

The potentiometer of a butterfly valve is located in the executive mechanism of a butterfly valve and gives the control unit information on the current coal of provision of a butterfly valve. The second potentiometer gives the control unit information on basic value and forms a spare signal at failure of a potentiometer of a butterfly valve.

The sensor 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.

Sensors of temperature of cooling liquid it is located in the thermostat case. It represents the resistor with negative temperature coefficient which resistance decreases with growth of temperature.

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

The system of ventilation of the fuel tank consists of an adsorber and the electromagnetic valve. In an adsorber the fuel vapors which are formed as a result of fuel heating accumulate. During the operation of the engine of couple are sucked away from an adsorber and move in engine 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 of a detonation is screwed in the block of cylinders, near the directing tube. It interferes with emergence of dangerous shock combustion of fuel mix. Thanks to it the moment of ignition can keep on detonation border that provides effective use of energy of combustion of fuel and by that reduces fuel consumption.