4. Power supply system

General information

All engines except for early models (518), are equipped with electronic system of injection of fuel.

Early models 518 are equipped with Solex carburetors. It is applied or the Solex 2B4 carburetor (early models), or 2 (late models). The mechanical fuel pump is put in action by an eccentric cam of the camshaft.

Models with injection of fuel are equipped with either fuel system of injection L-Jetronic, or Motronic. Since 1988 models with injection of fuel are equipped with the Motronic system applied so far - easy to distinguish this system from earlier on lack of an injector of cold start. The electric fuel pump is located under a back of the car or in the fuel tank. The relay of the fuel pump on the Motronic system turns on the low level of a signal from the Motronic (ECV) control unit. The fuel pump after inclusion of ignition turns on for several seconds and further works only during the operation of the engine.

System of an admission of air

The system of an admission of air consists of the case of the air filter, the measuring instrument of a stream of air and the case of a throttle (model with injection) and the inlet pipeline. In this Chapter all components, except for the inlet pipeline are considered; for data on removal and installation of the inlet pipeline address the Part the Repair work which is carried out without extraction of the engine from the car.

The throttle valve in the case of a throttle is put in action by an accelerator cable. When pressing an accelerator pedal the butterfly valve opens and the stream of air in system increases.

In systems of injection of fuel the gate in the batcher of air opens more widely and the stream of air increases. The sensor of provision of a throttle installed on a gate axis measures a corner of position of the gate (as far as it opens) and will transform this size to tension which is transferred to the computer.

Fuel system

On carburetor models the fuel pump gives to the carburetor fuel under pressure.

The needle valve in the float-operated camera supports the constant level of fuel. On channels of return of fuel system surplus of fuel comes back to the fuel tank.

On models with fuel injection the electric fuel pump gives fuel to the highway with constant pressure. The electric fuel pump on late models is located in the fuel tank or near a tank on early models. Early models are also equipped with the intermediate pump located in the fuel tank. The intermediate pump operates as auxiliary more powerful main pump during creation of necessary pressure. Pressure in fuel system the fuel pressure regulator operates. The fuel system also has a damper of pulsations of pressure, close to the fuel filter. The damper reduces pressure pulsations caused by operation of the fuel pump and opening - closing with an injector. The amount of fuel injected into ports of an admission precisely is defined by an electronic control unit (ECV or the computer). Some late models 5 of a Series have the fuel cooling device in the line of return.

Electronic control system (system of injection of fuel)

Except serial opening of injectors as it is described above, the electronic control unit carries out some other the tasks connected with control of fuel system and system of release. The block carries out these tasks, using data which arrive from a large number of the information sensors located in a motive compartment, comparing these data with information in memory and changing power setting, operating various devices. The majority of works on diagnostics of malfunctions and to repair of an electronic control system due to the need are in the special equipment outside the mechanic's opportunities - the fan. Additional data and procedures of testing of components of system of release (the sensor of concentration of oxygen, the cooler temperature sensor, the EVAP system and others) are provided in the Head of the Control system of the engine and decrease in toxicity of the fulfilled gases.