Releasing Pressure on High Pressure Side

Releasing Pressure on High Pressure Side

CAUTION!
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, e.g. removing high pressure pump, fuel rail, injectors, fuel pipe or fuel metering valve (N290) or fuel metering valve 2 (N402), the fuel pressure on the high pressure side must be reduced to a residual pressure of 6 bar. The procedure for this is as follows:

- Disconnect connector from the fuel metering valve (N290) on the right side of the high pressure pump - arrow -.





- Then disconnect connector from the fuel metering valve 2 (N402) on the left side of the high pressure pump - arrow -.





- Allow engine to idle approximately 10 seconds.

• If the fuel metering valve electrical connectors are disconnected in idle, the pressure on the high pressure side drops to approximately 6 bar.

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

- Switch off ignition.

CAUTION!
Fuel lines are pressurized! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before opening the high pressure system, place a cloth around the connection.

- Place a clean cloth around the connection point and carefully open the connection in order to release the residual pressure of approximately 6 bar. Draining fuel will be absorbed by the cloth.

- To conclude work, check Diagnostic Trouble Code (DTC) memory of Engine Control Module (ECM) (J623), erase all DTC entries which may have occurred from removing the connector.

• If DTC memory was erased, generate readiness code. Refer to "Guided Fault Finding".