Fuel pump control unit, function - GF47.20-P-4009-02MC
ENGINE 275.982 in MODEL 216, 221 up to Model Year 8
AMG vehicles work with a variable system pressure of 3.6 to 5.0 bars. The system pressure is regulated according to performance requirement and outside temperature in such a way that a rapid reaction characteristic is guaranteed for the engine in all load ranges.
The fuel pump control unit actuates the powerful Fuel pump (3 windings) for fuel pressure control via 3 phase offset PWM signals. The specified fuel pressure is received by the fuel pump control unit via the PWM signal at PIN 1 of the ME control unit. If the system pressure detected by the fuel pressure sensor drops below approx. 3.8 bar, the switch-on time of the PWM signal is extended. Power consumption, RPM and delivery rate of fuel pump increases.
The signal from the fuel pressure sensor with the current fuel pressure is read in at the ME control unit. The fuel pressure is checked for plausibility and then transmitted as a specified fuel pressure via the PWM signal at PIN 1 to the fuel pump control unit.
Switching on of the fuel pump takes place via the signal at Pin 2.
The voltage supply to fuel pump control unit at circuit 30 takes place fused from the rear SAM control unit with fuse and relay module (fuse 128, 25 A).
Various limp-home functions ensure fuel supply.
- If the PWM signal at PIN 1 fails the fuel pump control unit goes into limp-home mode. A fuel pressure is specified.
- If the PWM signal at PIN 2 fails the fuel pump will no longer be actuated by the fuel pump control unit.
The fuel pump control unit has a fault memory which can read out using STAR DIAGNOSIS.
The fuel pump control unit must be variant coded after being replaced.
The control unit must be screwed to the heat dissipation unit.