High Side Fuel Pressure, Releasing

High Side Fuel Pressure, Releasing

Special tools, testers and auxiliary items required

• Assembly Tool (T10118)


The fuel injection system is separated into a high pressure side where the pressure is a maximum of approximately 120 bar and a low pressure side where the pressure is approximately 6 bar.

Before opening the high pressure side, for example to remove the fuel pressure sensor (G247) , the fuel pressure must be reduced to a residual pressure of approximately 6 bar. The procedure for this is as follows.

- Disconnect the electrical connector - 1 - from the fuel pressure regulator valve (N276) using the assembly tool (T10118).






- Allow the engine to idle approximately 10 seconds.

• When the fuel pressure regulator valve electrical connector is disconnected during idle, 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, otherwise the pressure increases again due to the warming of the fuel.

- Turn off the ignition.


Fuel lines are pressurized! 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.

- To complete the procedure, check the Engine Control Module (ECM) Diagnostic Trouble Code (DTC) memory and erase all DTC entries which may have been caused by disconnecting the connector.

• If the DTC memory was erased, the readiness code must be generated again. Refer to "Guided Fault Finding" in the vehicle diagnostic tester.