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

ENGINE 642.8 as of 12/1/09 in MODEL 207.3/4 

ENGINE 642.8 as of 9/1/09 in MODEL 212.0/2 

ENGINE 642.8 in MODEL 204.0/2/9 

ENGINE 642.8 in MODEL 218 

ENGINE 651.9 as of 6/1/09 in MODEL 204.0/2/3/9 

ENGINE 651.9 as of 9/1/09 in MODEL 212.0 (except 212.098), 212.2 (except 212.298) 

ENGINE 651.9 in MODEL 207.3/4 

ENGINE 651.9 in MODEL 218 

View of right rear compartment door sill, on model 204 

Fig 1: Fuel Pump Control Unit - Shown On Model 204

Courtesy of MERCEDES-BENZ USA

Location 

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

Shown: rear seat area without rear bench seat on model 207 

Fig 2: Fuel Pump Control Unit - Shown On Model 207

Courtesy of MERCEDES-BENZ USA

Location 

The fuel system control unit is located in the middle under the rear bench seat.

Shown: rear door sill on the right on model 212.0 to model year 14/YoM 13 facelift 

Fig 3: Fuel Pump Control Unit - Shown On Model 212.0

Courtesy of MERCEDES-BENZ USA

Location 

On model 212 and model 218, the fuel pump control unit is located below the paneling on the right rear door sill.

Task 

The fuel system control unit is supplied by the "Continental Automotive GmbH" company and bears the internal designation FSCM-light (F  uel S  ystem C  ontrol M  odule-light).

The fuel system control unit regulates the fuel pump (M3) in accordance with requirements and transmits information about the current fuel pressure to the CDI control unit (N3/9).

Input and output signals 

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

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

Direct input signals 

• Circuit 15
• Circuit 30
• Circuit 31
• "Fuel pump ON" ground signal
• Fuel pressure sensor signal (B47) (model 204, 207, 212) or fuel pressure sensor (B4/7) (model 218)

Direct output signals 

• Power supply (5 V) fuel pressure sensor or fuel pressure sensor
• Fuel pressure sensor or fuel pressure sensor ground
• Fuel pump (12 V) (pulse width modulated signal (PWM signal)) (Plus)
• Fuel pump (PWM signal) (minus)

CAN input signals 

• Fuel pump ON
• Specified fuel pressure

CAN output signals 

• Fuel pressure
• Diagnostic data

Body 

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

Function 

The function description is subdivided into 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 from the CDI control unit as a CAN signal via the drive train CAN (CAN C) and as a ground signal. The fuel system control unit also receives the CAN signal "fuel requirements" from the CDI control unit.

The FSCU detects the current fuel pressure based in the voltage signal from fuel pressure sensor or fuel pressure sensor and transmits this information via the drive train CAN to the CDI control unit. The fuel system control unit evaluates the current fuel pressure, compares it with the specified fuel pressure and actuates the fuel pump by means of a PWM signal in such a way that the actual value corresponds to the specified value. In this manner, the fuel pressure is regulated to approx. 4.0 bars, depending on the fuel requirement.

The maximum feed volume at 12 V supply voltage and charged fuel filter is:

• 165 l/h for engine 642.8
• 180 l/h for engine 651.913/925
• 155 l/h for engine 651.9 except 651.913/925

Fuel system limp-home mode control unit 

• If the signal "fuel requirements" is missing a substitute value is created by the fuel system control unit and the fuel pump is actuated appropriately.
• If the signal "fuel requirements" and the signal from fuel pressure sensor or fuel pressure sensor are missing, the fuel pump is actuated by an established permanent pulse width modulation signal (maximum delivery).
• If both signals "Fuel pump ON" are missing, the fuel pump is actuated upon recognition of "circuit 15".
• Various limp-home functions ensure that the fuel supply is also provided if the internal controller fails (e.g. processor failure).

Diagnosis 

The fuel pump control unit conducts an own and component check. Recognized errors are stored by the fuel system control unit and sent to Xentry Diagnostics via the diagnostic CAN to the CDI 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
• Duty cycle of the PWM signal to 100 %

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

For vehicles as of 06/10 there is a powerful heating element rated at 600 watts installed in the fuel filter. The condensate which has gathered in the fuel filter an also be pumped off via a drain pipe.

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.