Fuel Pump Control Unit: Description and Operation

GF47.40-P-2001CY Component Description For The Fuel Pump Control Unit
- ENGINE 272.911 in MODEL 204.0 up to Model Year 8
- ENGINE 272.921 in MODEL 204.0 /2 up to Model Year 8
- ENGINE 272.947 in MODEL 204.0 /2 up to Model Year 8
- ENGINE 272.948 in MODEL 204.0 up to Model Year 8
- ENGINE 272.961 in MODEL 204.0 /2 up to Model Year 8
- ENGINE 272.971 in MODEL 204.0 up to Model Year 8





Location
N118 Fuel pump control unit

The fuel pump control unit is located under the panel for the door sill on the right rear.

Task
The fuel pump (M3) is actuated and regulated by the fuel pump control unit.

Function
Switching on of the fuel pump takes place if the signal "Fuel pump ON" is received by the fuel pump control unit. This signal is sent as a discrete signal (signal with a specific voltage value) and as a CAN signal by the ME-SFI [ME] control unit (N3/10) via the drive train CAN (CAN C) (redundant).
The fuel pump control unit receives the CAN signal "fuel requirements" from the ME-SFI [ME] control unit via a PWM signal (pulse width modulated signal) to regulate the fuel pump.
The current fuel pressure detects the fuel pump control unit via the fuel pressure sensor (B4/7). The information is also sent about the current fuel pressure by the fuel pump control unit to the ME-SFI [ME] control unit.

The fuel pump control unit evaluates the current fuel pressure and specification of the fuel requirements and actuates the fuel pump appropriately.
The fuel delivery amount is regulated variably from 0 to 130 l/h at a fuel pressure of 3.8 bar according to the fuel requirements.

Limp-home fuel pump control unit
- If the signal "fuel requirements" is missing a substitute value is created by the fuel pump control unit and actuates the fuel pump accordingly.
- If the signal "fuel requirements" is missing and also the signal from the fuel pressure sensor the fuel pump is actuated by a fixed permanent PWM signal (maximum delivery = 130 l/h).
- If both signals "fuel pump ON", the fuel pump is actuated upon recognition of "circuit 15".
- Various limp-home functions ensure that the fuel supply is also ensured for failure of the internal control (e.g. failure of the data processor).

Tanking service
The fuel tank can be emptied via the fuel pump control unit without the engine running.
The tanking service must be called up for this using the DAS and the following parameters entered:
- Parameter 01 for "fuel pump ON"
- Time "0-99999" seconds
- Duty cycle of the PWM signal up to 100%

During emptying the DAS must be connected and the ignition must remain switched on.

Input signals:
- Terminal 15
- Circuit 30
- Circuit 31
- Discrete signal "fuel pump ON" (from ME-SFI [ME] control unit)
- CAN signal "fuel pump ON" (from ME-SFI [ME] control unit)
- CAN signal "fuel requirements" (from ME-SFI [ME] control unit)
- Signal from fuel pressure sensor

Output signals:
- Fuel pressure sensor + (5 V)
- Fuel pressure sensor -
- Fuel pump + (12 V) PWM signal
- Fuel pump - PWM signal