Component Description For Fuel Pump Control Unit - GF47.40-P-2001MRS
Engine 264.9 in Model 205, 253
Shown: Model 205.0
Location
The fuel system control unit is located under the trim of the rear right door sill (Model 205.0/1/2, Model 253) or behind the side trim in the right rear passenger compartment (Model 205.3/4).
Tasks
The fuel system control unit has the internal designation FSCM-GEN4 (Fuel System Control Module GENeration 4.
The fuel system control unit regulates the fuel pump (M3) in a demand-oriented manner. To do so, the fuel system control unit evaluates various input signals.
Input signals via direct lines
- Signal "Fuel pump ON"
- Sensor signal of left fuel tank fuel display fill level sensor (B4/1) (with code 915 (fuel tank with increased capacity) or code 916 (fuel tank 66 l))
- Sensor signal from fuel tank fuel level indicator fill level sensor, right (B4/2)
- Fuel pressure sensor sensor signal (B47)
Input signals via drive CAN (CAN C1)
The fuel system control unit receives, for example, the following signals via the drive CAN:
- Terminal status of terminal 15
- Fuel system ON
- Fuel specified pressure
- Engine running status
- Engine torque
- On-board electrical system status
- Accelerator pedal position
The fuel system control unit evaluates all relevant input signals and actuates the fuel pump with three phase-offset AC voltage signals:
- Alternating voltage phase U
- Alternating voltage phase V
- Alternating voltage phase W
Output signals via the drive CAN
The fuel system control unit transmits, for example, the following signals via the drive CAN:
- Fuel pressure
- Fuel pump status
- Fuel tank fill level
- Status of fuel system
- Diagnostic data
After the fuel system control unit has been exchanged, variant coding must be carried out.
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 transmitted redundantly directly as a ground signal by the ME-SFI control unit via the drive CAN. 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-SFI control unit. In order to control the fuel pump the ME-SFI [ME] control unit evaluates the fuel pressure and the load request and adjusts the requested fuel pressure over an integral controller through actuation of the fuel pump.
The low fuel pressure is controlled to between approx. 4 to a maximum of 6.7 bar, depending on the fuel temperature and the Engine speed.
Limp-home mode
Limp-home functions for drive CAN and fuel pressure sensor failure are stored in the fuel system control unit:
- Upon failure of the drive train CAN the signals "fuel pump ON" and "terminal 15" are redundantly sent over a direct line from the ME-SFI [ME] control unit to the FSCU. The fuel pump regulates the pressure to a substitute value stored in the FscU.
- For failure of the fuel pressure sensor the fuel pump is actuated over fail safe characteristics curve in the FSCU.
- If both the drive CAN and the fuel pressure sensor fail, the fuel pump is actuated with a voltage stored in the fuel system control unit.
Fuel tank fill level
The FSCU determines the current resistance of the fuel level indicator fuel tank fill level sensor over a voltage measurement and therefore the fill level of the fuel.
The determined voltage value is compared with a characteristic stored in the FSCU which is dependent on the fuel tank volume. The fuel system control unit calculates as a result the capacity of the fuel tank and performs a plausibility test. In this connection, the capacity of the fuel tank is compared with the current Engine fuel consumption.
The values of the plausibility test are transmitted in liters and as a percentage to the instrument cluster (A1). Upon reaching the reserve quantity, a signal is transmitted to the instrument cluster, which them issues a warning message.
Tank drainage service
The fuel tank can be emptied over the FSCU without the Engine running.
To do this, the tank draining service must be called up with the diagnostic tester, and the following parameters must be entered:
- Parameter 01 for "fuel pump ON"
- Time: 0 to 99, 999 s
- Specified fuel pressure 5.5 bar
During emptying the ignition must remain switched on.
| Wiring diagram for FSCU | Engine 264.9 in Model 205 | PE47.40-P-2101-97FBB | |
| Engine 264.9 in Model 253 | PE47.40-P-2101-97FCA |