Location
The fuel pump (1) is located on the fuel high-pressure pump.
Task
The fuel pump (1) suctions the fuel out of the fuel tank via the fuel filter module, and supplies the fuel high-pressure pump with the required fuel quantity in all operating statuses of the engine.
Shown on engine 471.9 |
1 | Fuel pump (FP) |
A | Fuel feed intake side |
B | Fuel feed (thrust side) |
W47.20-1083-76
Structure
2 | Fuel inlet |
3 | Bypass valve |
4 | Fuel outlet |
5 | Pressure limiting valve |
A | Fuel feed intake side |
B | Fuel feed (thrust side) |
W47.20-1061-81
Function
The fuel pump (1) is designed as a gear pump and is actuated via the fuel high-pressure pump.
As soon as the engine is started or is running, the right gearwheel in the fuel pump (1) is actuated via a driver on the camshaft of the fuel high-pressure pump.
Because the teeth of the right gearwheel engage in the teeth of the left gearwheel, the latter turns in the other direction at the same time.
Due to the rotation of both gearwheels and the design of the pump chamber, the fuel is suctioned via the fuel inlet (2) and delivered along the inside wall of the pump to the fuel outlet (4).
In the course of this, the fuel is compacted until the necessary fuel or system pressure is reached.
The max. permissible system pressure that can already be reached at idle speed is determined by the opening pressure of the pressure limiting valve (5).
When the system or opening pressure is reached and the pressure limiting valve (5), which is designed as an overflow valve, is open, the fuel feed on thrust side (B) is short circuited with the fuel feed on intake side (A) via a channel, so that no further pressure buildup can take place.
For the event that a fuel system is filled externally, the bypass valve (3) is installed through which the fuel flows past the stopped gearwheels and to the thrust side fuel feed (B).