The pressure-controlled fuel supply system with variable system pressure is handled by an electrical fuel pump. The DME determines the requirement from the fuel-pressure sensor signal and the operating status of the engine. The DME sends the volume of fuel request as a CAN message across the Local-CAN to the fuel pump control.
The fuel pump control converts the volume of fuel request into the activation of the fuel pump. The fuel pump is driven via an electrically commutated 3-phase electric motor. The value of the CAN message lies in the range between 0 and 100 % The fuel pump control uses a characteristic curve to convert this value into a fuel pump speed and sets this speed at the fuel pump.
With full activation of the electrical fuel pump, the fuel delivery pressure is limited by the mechanical pressure regulator in the fuel tank to 6.2 bar.
For diagnosis functions of the DME, the fuel pump control must send the following data via the Local-CAN to the DME:
When terminal 15 is switched on, the electric fuel pump only starts up if the engine has been parked for a longer period.
The electric fuel pump is monitored by the fuel pump control. If the fuel pump control detects faults, the fuel pump control reports the faults to the DME via the Local-CAN. The faults are stored in the DME.
If faults are detected in the fuel supply system, the fuel pump is run in emergency operation, i.e. the fuel pump is operated with 100 % activation.
The fuel system is airtight, i.e. the pressure is maintained after stopping the engine. After one hour, at least 1 bar must be maintained.