Fuel Injector: Description and Operation

16 00 - General function description for fuel supply systems

Fuel supply systems, spark-ignition engines



Fuel system

The electric fuel pump in the fuel tank generates the pressure in the fuel system which is set by the pressure regulator to a specific level.

Tank venting system

The tank venting system is an enclosed system which is vented via a carbon canister. The carbon is incorporated in the carbon canister as granulate. The large surface of the carbon stores the fuel vapors which occur in the fuel tank. The carbon canister must be regenerated on a regular basis so as to be able to continue storing fuel vapors. Regeneration is performed by way of purging with fresh air via the intake manifold. This process is controlled by the engine control unit.

Fuel supply systems, diesel engines



Fuel system

The electric fuel pump in the fuel tank supplies the engine with fuel. Two types of high-pressure pump are used for cylinder injection.

1. The distributor injection pump supplies each cylinder directly with fuel via the corresponding injection nozzle.

2. The high-pressure pump for the common rail systems generates in the fuel rail the necessary pressure for all the injection nozzles.

In common rail systems, a further pump (inline pump, M57/gear pump, M67) is connected between the high-pressure pump and the electric fuel pump. This pump supports the fuel pump in the fuel tank in the event of a high fuel demand.

Tank venting system

Diesel fuel is non-volatile and therefore a carbon canister is not required. The fuel tank is vented directly to atmosphere.