Fuel Pump: Description and Operation
GF47.20-P-2000SM Component Description Of Fuel Pump
- ENGINE 113.986 in MODEL 215, 220
- ENGINE 113.987 in MODEL 209
- ENGINE 113.988 in MODEL 203 up to Model Year 8
- ENGINE 113.989 in MODEL 171 up to Model Year 8
Picture on the left: Two-stage flow pump in model 203, 209
M3 Fuel pump
The fuel pump is located at the bottom in the right fuel tank chamber.
Picture on the right: Helical spindle pump in model 215, 220
M3 Fuel pump
The fuel pump is located below the fuel tank on the vehicle chassis.
Two-stage flow pump model 171
M3 Fuel pump assembly
The fuel pump assembly is located at the bottom in the fuel tank.
Task
The fuel pump supplies an adequate quantity of fuel at the required pressure to the fuel injection system (fuel distribution tube).
Design of screw spindle pump
1 Rotating spindle
2 Drive spindle
3 Check valve
4 Pressure relief valve
5 Electric motor
6 Ground connection
7 Voltage supply
a Fuel from the fuel tank
b Fuel to the fuel filter
Function of helical spindle pump
The rotating spindle (1) delivers the fuel to the fuel filter by the centrifugal force effect. 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 circulation relatively cool fuel is always available for injection (avoids the formation of vapor bubbles).
A pressure relief valve (4) is integrated in the fuel pump in order to limit the pressure.
The check valve (3) in the fuel pump decouples the fuel system from the fuel tank by preventing fuel from flowing back through the disconnected fuel pump to the fuel tank.
Fuel pump control
MODEL 171
The fuel pump assembly (M3) is controlled via the fuel pump relay (N10/2kA) by the ME control unit (N3/10).
Model 203, 209
The fuel pump (M3) is controlled via the fuel pump relay (N10/2kA) by the ME control unit (N3/10).
Model 215, 220
The fuel pump (M3) is controlled via the fuel pump relay (K40/5kT) by the ME control unit (N3/10).