Mercedes M-Class W163

since 1997 release

Repair and operation of the car

Power supply system of diesel engines

General information

During the operation of the diesel engine in its cylinders external air which compresses to high pressure is soaked up. At the same time air temperature as a result of adiabatic heating rises to the value of 700-900 °C exceeding temperature of ignition of diesel fuel. Fuel is injected into the cylinder with some advancing and ignites. Thus, spark plugs for ignition of fuel are not used.

For reduction of maintenance of toxic components in the fulfilled gases diesel models are equipped with the special oxidizing catalytic converter. At the same time the system of recirculation (EGR), due to the dosed admixture to the air of a small amount of the fulfilled gases which is soaked up in the engine and, - as a result, - decrease in concentration in gas mixture of oxygen, provides essential decrease in contents in products of combustion of oxides of nitrogen _(NOX). Due to functioning of the EGR system leads to reduction of a delay of ignition and decrease in temperature of combustion that as a result leads to formation reduction _{of NOX}. An indispensable condition at the organization of recirculation is admixture dosage accuracy, otherwise the content in the fulfilled gases of firm particles of carbon (soot) increases. The amount of the air which is soaked up in the engine is defined by the special measuring instrument, given out which information allows the electronic module of management to exercise control of recirculation process.

The injection of fuel is made directly in combustion chambers of cylinders.

Functioning of the engine the electronic system, on structure and the principle of functioning similar to the control system of the engine applied on petrol models by petrol engines operates. The data arriving from the whole set of the information sensors which are continuously tracing operational parameters form the basis of the teams developed by the module of management.

Information on position of the crankshaft and speed of rotation of the engine comes to the control unit from the sensor of position of the crankshaft (CKP). The inductive head of the sensor is located opposite to a flywheel and constantly scans the special basic tags applied on a surface of the last. When passing a tag by a sensitive element of a measuring head the sensor develops the alarm impulse given on the module of management. Tags are evenly applied on a flywheel surface, except for the only admission corresponding to situation 90 ° before VMT of the piston of the first cylinder. At the time of passing by a flywheel of this point the alarm impulse is not given for the module of management that allows the last to define VMT moment. On length of pause/porosity of impulses the module obtains information on the frequency of rotation of a bent shaft.

Information on quantity and temperature of the air coming to the engine arrives from sensors of absolute pressure in the inlet pipeline (MAP) and temperatures of the soaked-up air (IAT). The MAP sensor is connected by a vacuum hose to the inlet pipeline and measures depression depth in the last. For control of temperature of the soaked-up air two IAT sensors, one of which is established ahead of a turbocompressor, another - behind the Intermediate cooler (intercooler) are used. The readings taken by sensors are used by the module of management when calculating exact amount of fuel which has to be injected into engine combustion chambers.

The traditional sensor of temperature of cooling liquid is replaced with the block head temperature sensor supplying the module of management of information which is used at corrections of quality of air-fuel mix and calculation of the moments of injection. Besides, the data which are taken off by the sensor are used at management of functioning of system of preliminary warming up of the cold engine.

The sensor switch of stoplights/provision of a brake pedal informs the control unit on the current provision of a pedal of a foot brake. When receiving signals from these sensors the control system instantly transfers the engine to the mode of idling and supports him to the moment of receipt of a signal from the sensor of position of the accelerator pedal.

The fuel supply system is organized according to the scheme of direct injection. The vortex cameras providing twisting of the fuel injected into combustion chambers of cylinders are provided in the bottoms of pistons. Opening of nozzles is made for fuel combustion process optimization in two steps (for this purpose in each nozzle about two springs are placed). When opening the working valve of a nozzle a small part of fuel gets on internal components of the last, providing their greasing, then comes back to the fuel tank.

Control of preliminary warming up is also exercised by the engine management module which at the cold engine provides a certain shift of the moment of injection. Besides, the module of management controls process of functioning of candles of an incandescence. Glow plugs are screwed in each cylinder, are activated before start of the engine and remain in a hot state during the whole time of a provorachivaniye of a bent shaft a starter, and also some time after start of the engine. Application of candles of an incandescence allows to facilitate considerably start of the engine in cold weather. The special, built-in in a combination of devices control lamp warns about activation of candles of the driver (see the Head Governing bodies and methods of safe operation), - as soon as the lamp goes out, it is possible to start start of the engine. In especially cold weather, candles continue to function still some time after start, maintaining stability of turns of the engine and providing decrease in toxic components in combustion products.

The design of modern diesel engines differs in the increased efficiency of start therefore need for application of candles of an incandescence arises only at air temperatures below - 10 °C.

The fuel pumped preliminary fuel is passed via the fuel filter where its cleaning of impurity of moisture and other pollution is made, try to treat honestly maintenance performing procedures, in due time making replacement of the filtering element.