Fuel Pump Control Unit: Description and Operation

GF47.40-P-2001MOR Component Description For The Fuel Pump Control Unit
- ENGINES 275.954 in MODEL 230.477 as of Model Year 09 / AEJ 08 model refinement package
- ENGINES 275.981 in MODEL 230.479 as of Model Year 09 / AEJ 08 model refinement package





View of underfloor
M3 Fuel pump
N118 Fuel pump control unit

Location
The fuel pump control unit is located in the underfloor behind the rear axle.

Task
The fuel pump control unit actuates the fuel pump as required.

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

To control the fuel pump, the ME-SFI control unit sends the"specified fuel pressure" PWM signal to the fuel pump control unit (with a duty cycle of 10 to 90 %). This control unit evaluates the PWM signal and the current fuel pressure through the pressure sensor fuel (B4/7), and actuates the fuel pump accordingly.

Depending on fuel requirements, the fuel pump delivery rate is set with a constant fuel pressure of about 3.8 bar for engine 275.954 and 4.1 bar for engine 275.981 (AMG).

Emergency running
If the "specified fuel pressure" is missing or implausible, the fuel pump is actuated with a duty cycle of 100 % (maximum delivery rate).