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.