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

Engine 651.9 in model 205 (except 205.012/212), 253 

Shown: Model 205.0 

Fig 1: Identifying Fuel System Control Unit - Shown On Model 205.0
G10133586Courtesy of MERCEDES-BENZ USA

Location 

The fuel system control unit is located under the trim of the right rear rocker panel.

Tasks 

The fuel system control unit is supplied by the Continental Automotive GmbH company and bears the internal designation FSCM (GEN4 F  uel S  ystem C  ontrol M  odule Generation 4).

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 FSCU and the respective output signal is issued:

Direct input signals 

Direct output signals 

CAN input signals 

CAN output signals 

Body 

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

Function 

The function description is subdivided into the following points:

Controlling the fuel pump 

Switching on of the fuel pump takes place if a "fuel pump ON" signal is received by the FSCU. This signal is sent redundantly by the CDI control unit as a CAN signal via the drive train CAN (CAN C1) 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 CDI control unit. In order to control the fuel pump the CDI control unit evaluates the fuel pressure and the load request and transmits the pulse width modulated signal "fuel specified pressure" to the FSCU. This evaluates the PWM signal and actuates the fuel pump with a phase-shifted alternating current as required, so that the actual fuel pressure corresponds to the specified value. The fuel pump pressure is controlled dependent on the fuel temperature and the engine RPM between about 4.5 to a maximum of 6.7 bar.

Fuel system control unit limp-home mode 

Fill level evaluation of fuel tank 

The FSCU reads signals from the fuel tank fuel level indicator fill level sensor to compute and evaluate the fill level of the fuel tank.

The nominal volumes of the fuel tank, the current fill level in percent and the reserve quantity are calculated from the values measured in ohms and transmitted to the CDI control unit with an appropriate signal. Furthermore the fill level sensors are checked for plausibility. In the event of implausible measurements, a fault message is sent to the CDI control unit.

Diagnosis 

The FSCU performs am own and component check.

Recognized faults are stored by the FSCU and made available via the drive train CAN to the CDI control unit and additionally via the diagnostic CAN (CAN D) to attached diagnostic equipment.

Tank drainage service 

The fuel tank can be emptied over the FSCU without the engine running. To do this, the container draining function is selected using Xentry Diagnostics, and the following parameters are entered:

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 FSCU. After replacement of the FSCU a variant coding must be carried out. The fuel system control unit is Star2-capable.

  Wiring diagram for FSCU N118 PE47.40-P-2101-97FBA 
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