Fuel pump function - GF47.20-P-4003-02A
(Roller cell pump)
The fuel pump is designed as an electrically operated roller cell pump. The eccentrically arranged rotor disc (7) in the pump housing features metal rollers (8) around its circumference, which are mounted in slot-shaped recesses, and which are pressed against the pump housing (9) by the centrifugal force when the pump rotates. The rollers act as a continuous seal. The fuel is moved in the cavities which form between the rollers.
A pumping effect is produced as a result of the fact that the rollers, after shutting off the feed drilling (10), push the entrapped quantity of fuel as they rotate until the fuel leaves the roller cell pump through the drain drilling (11).
The fuel pump supplies more fuel than the maximum requirement of the engine in order to maintain the pressure in the fuel system in all operating states. As a result of this circulation, the fuel which is available for injection is always relatively cool (avoids the formation of vapor bubbles).
The fuel pump is actuated:
- ignition ON (about 1-2 sec.)
- when the starter is operated (circuit 50)
- when the engine is running (TN)
A pressure relief valve (2) is integrated in the fuel pump in order to limit the pressure. The check valve (6) in the fuel pump decouples the fuel system from the fuel tank by preventing fuel from flowing back to the fuel tank through the fuel pump when the engine is switched off.