Component description for fuel pump control unit - GF47.40-P-2001MMA

ENGINE 157.9 in MODEL 212, 218 

View of right rear compartment door sill, model 218 

Fig 1: Fuel System Control Unit - Shown On Model 218

Courtesy of MERCEDES-BENZ USA

Location 

The fuel system control unit is located under the trim of the right rear door sill.

Task 

The FSCU carries the internal designation UFPC AMG (U  niversal F  uel P  ump C  ontroller for AMG).

The fuel system control unit regulates the fuel pump (M3) according to need and transmits information via the current fuel pressure to the ME-SFI [ME] control unit (N3/10).

Input and output signals 

The following input signals are evaluated by the fuel system control unit and appropriate output signals are emitted:

• CAN input signals 
• CAN output signals 
• Direct input signals 
• Direct output signals

CAN input signals 

• Fuel pump ON
• Data for variant coding

CAN output signals 

• Fuel supply status
• Diagnostic data

Direct input signals 

• Circuit 15
• Circuit 30
• Circuit 31
• "Fuel pump ON" ground signal
• Fuel pressure sensor signal (B4/7) (model 212), fuel pressure sensor (B4/7) (model 218)

Direct output signals 

• Fuel pressure sensor (5 V), (model 212), fuel pressure sensor (model 218)
• Fuel pressure sensor mass (model 212), fuel pressure sensor (model 218)
• AC signal for fuel pump (phase A)
• AC signal for fuel pump (phase B)
• AC signal for fuel pump (phase C)

Body 

The fuel system control unit consists of a fuel housing with two plugs and internal measuring and control electronics.

Function 

The function is described at the following points:

• Fuel pump regulation 
• Fuel system limp-home mode control unit 
• Diagnosis 
• Tank-draining function 

Fuel pump regulation 

Switching on of the fuel pump takes place if a signal "fuel pump ON" is received by the fuel system control unit. This signal is sent redundantly by the ME-SFI [ME] control unit as a CAN signal via the drive CAN (CAN C) and directly as a ground signal.

The fuel system control unit detects the current fuel pressure by means of a voltage signal from the fuel pressure sensor and transmits this information via the drive train CAN to the ME control unit.

The fuel system control unit evaluates the current fuel pressure, compares it with the specified fuel pressure and actuates the fuel pump appropriately by means of these phase-offset AC voltage signals in such a way that the actual value corresponds to the specified value.

The fuel pump pressure is regulated dependent on the fuel temperature and the engine RPM between about 4.0 and a maximum of 6.7 bar.

Fuel system limp-home mode control unit 

• If the signal "Specified fuel pressure" is missing, a substitute value is created by the fuel system control unit and the fuel pump is appropriately actuated.
• If the signal from the fuel pressure sensor is missing the fuel pump is actuated over a consumption-dependent limp-home mode characteristics.
• If the signal "specified fuel pressure" and the signal from the fuel pressure sensor are missing, the fuel pump is actuated by an established replacement voltage.

Diagnosis 

The fuel system control unit conducts an own and component check. Recognized errors are stored by the fuel system control unit and sent to the Xentry diagnostics via the diagnostic CAN to the ME-SFI control unit via the drive train CAN.

Tank-draining function 

The fuel tank can be emptied over the fuel system control unit without the engine running.

To do this, the tank draining function is selected using Xentry Diagnostics, and the following parameters are entered:

• Parameter 01 for "Fuel pump ON"
• Time "0-99999" seconds
• Specified fuel pressure 5.5 bar

During draining, Xentry Diagnostics must remain connected and the ignition must remain switched on.

Variants 

The vehicle and engine variants are already stored in the fuel system control unit. After replacing the fuel system control unit, variant coding must be conducted.