Procedures
High Side Fuel Pressure, Releasing
Special tools, testers and auxiliary items required
• Assembly Tool (T10118)
The fuel injection system is divided into a high pressure side (maximum approximately 120 bar) and a low pressure side (approximately 6 bar):
• Before opening the high pressure side, for example, removing the high pressure pump, fuel rail, fuel injectors , fuel pipes or fuel pressure sensor, the high pressure side pressure must be reduced to a residual pressure of approximately 6 bar. The procedure for this is as follows:
- Using the assembly tool (T10118) , disconnect the electrical connector - 1 - from fuel pressure regulator valve (N276).
- Allow the engine to idle approximately 10 seconds.
• When the fuel pressure regulator valve electrical connector is disconnected during idle, the high side pressure decreases to approximately 6 bar.
• After the high pressure has been released, the high pressure system must be opened, otherwise the pressure increases again due to the warming of the fuel.
- Turn off the ignition.
The fuel lines are pressurized!
• For safety reasons, interrupt the current supply to the fuel pump, refer to => [ Safety Precautions ] Fuel Supply before opening the fuel system because the fuel pump is activated by the driver door contact switch.
• Always wear protective eyewear and protective clothing to prevent injuries and fuel from coming in contact with your skin.
• Before opening the high pressure side, place a cloth around the connection.
- Place a clean cloth around the connection point and carefully open to release the residual pressure of approximately 6 bar. Leaking fuel must be absorbed.
• By disconnecting the connections, Diagnostic Trouble Codes (DTCs) are stored to memory. After assembling, check the fault memory and erase, if necessary.
- Check the Engine Control Module (ECM) DTC memory and erase any entries. Refer to "Guided Function" in the vehicle diagnostic tester.
• If the DTC memory was erased, the readiness code must be generated again. Refer to "Guided Fault Finding" in the vehicle diagnostic tester.