Multiport Fuel Injection

Before Opening High Pressure Fuel Injection System


The fuel injection system is divided into a high pressure section (maximum approximately 120 bar) and a low pressure system (approximately 6 bar).

Before opening high pressure parts, for example removing high pressure pump, fuel rail, fuel injectors, fuel pipes, etc., reduce the fuel pressure in the high pressure area to a residual pressure of approximately 6 bar. The procedure for this is as follows.

Reducing High Fuel Pressure

- Connect the vehicle diagnosis tester.

- Start the engine and let it run at idle.

- Select engine electronics in "Vehicle Self-Diagnosis"

- Select diagnostic function measured values, display group "140".

- The fuel pressure is displayed in field "3".

• Specified value: between 35 and 45 bar.

- Remove the right instrument panel cover.






- Remove fuse 1 in the fuse carrier ST2 (brown) - 2 -.

• Ignore - 1 and 3 -.

- Follow the fuel pressure on the tester.

• The fuel pressure decreases rapidly because the mechanical high pressure pump is no longer supplied with fuel from the transfer fuel pump (G6).

- Switch off the ignition as soon as the fuel pressure has decreased to approximately 8 bar.

• The fuel pressure must not drop below 6 bar, because otherwise the engine will shut off (risk of catalytic converter damage).

The fuel rail will continue to be filled with fuel, but it will no longer be under high pressure.


Do not let fuel come into contact with skin.

• Wear protective eye-wear and clothing when opening the fuel system.

• Lay clean cloths around the connection before opening the high pressure area to collect any fuel that leaks out.

- Loosen the wire at a connection immediately.

• If the high pressure system is not opened immediately, the pressure will increase because of post-heating.

- Lay clean cloths around connectors and catch escaping fuel.

Final Procedures

- Install fuse 1 in the fuse carrier ST2 (brown).

- Install the right instrument panel cover.

- Install the fuse.

- Erase the DTC memory and generate the readiness code in the engine control module in "Guided Functions".