Fuel Pump: Description and Operation

GF47.20-P-2000MIR Component Description For Fuel Pump
- ENGINES 272.949 in MODEL 230.454 as of Model Year 09 /Modification Year 08 model refinement package
- ENGINES 272.968 in MODEL 230.458 as of Model Year 09 /Modification Year 08 model refinement package
- ENGINES 273.965 in MODEL 230.471 as of Model Year 09 /Modification Year 08 model refinement package





View of underfloor
M3 Fuel pump

Location
The fuel pump is located in the underfloor, on the right of the rear axle differential.

Task
The fuel pump supplied fuel in sufficient quantity and at the required pressure to the fuel injection system (fuel distribution rail).





Design
1 Rotating spindle
2 Drive spindle
3 Check valve
4 Pressure relief valve
5 Electric motor
6 Ground connection
7 Power supply (12 V)
a Fuel from fuel tank
b Fuel to fuel filter with integrated fuel pressure regulator

The fuel pump consists of a jack screw pump.

Function
The ME-SFI control unit (N3/10) actuates the fuel pump through the fuel pump relay (K40/5kT).

The fuel pump draws fuel from the bottom of the fuel tank swirl pot through a fuel strainer.
The rotating jack screw delivers fuel to the fuel filter by centrifugal force. In this case the fuel pump delivers more fuel than the engine needs in total in order to maintain the pressure in the fuel system in all operating states. As a result of this extra delivery circulation of fuel occurs whereby there is always relatively cool fuel is available at all times for injection (avoids the formation of vapor bubbles).

A pressure relief valve is integrated in the fuel pump to limit the internal pressure.
The check valve in the fuel pump decouples the fuel system from the fuel tank, by preventing the backflow of fuel to the fuel tank when the fuel pump is switched off.