Procedures

High Side Fuel Pressure, Releasing


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 (G247) - the fuel pressure in the high pressure side must be reduced to a residual pressure of approximately 6 bar. The procedure for this is as follows.

- Disconnect the electrical connector from the fuel pressure regulator valve (N276) - arrow -.






- Allow the engine to idle approximately 10 seconds.

• When the fuel pressure regulator valve electrical connector is disconnected during idle, the pressure in the high pressure side decreases to approximately 6 bar.

• After the high pressure has been released, the high pressure side must be opened immediately. Otherwise, the pressure can increase again due to the warming of the fuel.

- Turn off the ignition.


Fuel system is under pressure!

• Always wear protective eye-wear and protective clothing to prevent injuries and fuel from coming in contact with your skin.

• Before loosening line connections, place a cloth around the connection point. Then release pressure by carefully pulling off the line.

- 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.

- To conclude work, check the Diagnostic Trouble Code (DTC) memory of the Engine Control Module (ECM), erase all DTC entries which may have occurred from removing the connector.

• Generate a readiness code if the DTC memory was erased. Refer to "Guided Function" in the vehicle diagnosis, testing and information system VAS 5051.