Engine

Before Opening High Pressure Fuel Injection System

For safety reasons, if the battery is not disconnected, fuse S 81- B - from the fuel pump control module (J538) must be removed before opening fuel system. Otherwise, the fuel pump will be activated by the driver's door contact switch.





• Fuse S81 - B - is in the 9-pin relay and fuse carrier under the rear shelf (on the right side).

• By removing fuse S81 - B -, the voltage supply to terminal 30 for the fuel pump control module is interrupted.

CAUTION!
The fuel injection system is divided into a high pressure section (maximum approximately 125 bar) and a low pressure system (approximately 7 bar).

Before opening high pressure parts, for example removing high pressure pump, fuel rail, fuel injectors, fuel pipes or fuel pressure sensor (G247), fuel pressure in high pressure area must be reduced to a residual pressure of approximately 7 bar. The procedure for this is as follows.

High Fuel Pressure, Reducing

Special tools, testers and auxiliary items required

• Assembly Tool (T10118)

- Disconnect the electrical connector - 1 - from the fuel metering valve 2 (N290) on the right high pressure pump.





- Disconnect the electrical connector - 1 - from the fuel metering valve 2 (N402) on the left high pressure pump.





- Allow engine to idle approximately 10 seconds.

• The fuel pressure is reduced from approximately 23 bar to approximately 7 bar when the electrical connectors are disconnected at idle.

• The decreasing fuel pressure can be decreased if a vehicle diagnosis and service system. (VAS 5052) is connected and engine control module is selected. And select display group 140 under read measured value block function.

• Fuel pressure (actual value) is shown in display field 3.

- Switch off ignition.

CAUTION!
The fuel lines will continue to be filled with fuel, but will no longer be under high pressure. To open fuel system, wear protective eyewear and clothing to prevent injuries and contact with skin.

Before opening the high pressure system, place a cloth around the connection.

- After reducing high pressure, high pressure system can be opened. To do this, place a clean cloth around connection to reduce residual pressure in system to approximately 7 bar. Escaping fuel must be absorbed.

• If the high pressure line is not opened immediately, the fuel pressure can increase slightly.

- Connector (VAS 5052) and generate the readiness code in the engine control module in the guided fault finding operating mode.