Supply of fuel in line with requirements
| Index | Explanation |
|---|---|
| 1 | Rail pressure sensor |
| 2 | High-pressure pump with volume control valve |
| 3 | Electronic fuel pump |
| 4 | Fuel low-pressure sensor |
| 5 | Electronic fuel-pump control (EKPS control unit) |
| 6 | Digital engine electronics (DME) |
| 7 | Injectors |
| 8 | Rail |
| PT-CAN | Powertrain CAN |
| PT-CAN2 | Powertrain-CAN 2 (depends on model series) |
The low-pressure fuel sensor transmits a voltage signal to the engine-management control unit (DME control unit) indicating the system pressure between the electric fuel pump and the high-pressure pump. The low-pressure fuel sensor monitors system pressure (low-pressure fuel system) upstream from the high-pressure pump.
The DME control unit runs a continuous comparison between the specified pressure and actual pressure. If there is a deviation between the specified pressure and actual pressure, the DME control unit increases or decreases the voltage for the electric fuel pump, sent as a message across the PT-CAN to the EKP control unit. The EKP control unit converts the message into an output voltage for the electric fuel pump. These regulates the required delivery pressure for the engine (or high-pressure pump). In the event of a signal failure (fuel low pressure sensor), with terminal 15 On the electric fuel pump is operated with pre-control. If the CAN bus fails, the electric fuel pump is operated via the EKP control unit with the prevailing on-board supply voltage. The high-pressure pump raises the fuel pressure to between 50 and 200 bar. The high-pressure line delivers the fuel to the rail. In the rail, the fuel is stored temporarily, then distributed to the injectors. The rail-pressure sensor measures the current fuel delivery pressure in the rail. When the volume control valve in the high-pressure pump opens, the excess fuel delivered is returned to the inlet. If the high-pressure pump fails, restricted driving is possible.
Notes for Service department