Incorrect Fueling

Incorrect Fueling

Fueling incorrectly can cause insufficient lubrication which can lead to irreversible damage to the high pressure components, especially the high pressure pump. Damage in the form of seizing and particle abrasion can be expected. These particles will cause further damage in the pressure control valve and the injectors.

Two incorrect fueling scenarios are possible:

• Scenario 1: Incorrect fueling was noticed BEFORE starting the engine and the engine was NOT started. Refer to => [ Scenario 1 ].

• Scenario 2: Incorrect fuel was noticed AFTER starting the engine. Contaminated or incorrect fuel has entered the fuel system and reached the high pressure components. Refer to => [ Scenario 2 ].

Scenario 1

- DO NOT turn on the ignition.

- Empty the fuel tank as much as possible through the filler neck using the fuel extracting device (VAS 5190). Refer to => [ Fuel Tank, Draining ] Procedures.

- Disconnect the connector from the auxiliary fuel pump (V393) (in-line electric fuel pump) inside the engine compartment.

- Remove the rear seat bench.

- Remove the cover from the fuel delivery unit.

• Press in the securing ring to disengage the fuel line.

- Remove the fuel supply line, which is black or has a black mark, - A - from the fuel delivery unit.

- Connect the connector to the auxiliary fuel pump (in-line electric fuel pump) inside the engine compartment.

- Fill the fuel tank completely with diesel fuel.

- Perform a road test.

Scenario 2

- Empty the fuel tank as much as possible through the filler neck using the fuel extracting device (VAS 5190). Refer to => [ Fuel Tank, Draining ] Procedures.

- Remove the rear seat bench.

- Remove the cover from the fuel delivery unit.

• Press in the securing ring to disengage the fuel line.

- Remove the fuel return line, which is blue or has a blue mark, - B - from the fuel delivery unit.

- Connect the hose (VAS 6550/1) from the pressure tester (VAS 6550) to the fuel supply line - A -.

- Place the open end of the hose (VAS 6550/1) in a suitable container.

- Connect the vehicle diagnostic tester and perform the Guided Function "Check electrical fuel pumps".

• The fuel pump now runs for 30 seconds.

- Repeat this procedure as necessary until the fuel tank is completely empty.

- Remove the fuel delivery unit and check the fuel tank for contamination and shavings.

- Clean the fuel tank if necessary and install the fuel delivery unit.

- Fill the fuel tank with 5 liters of diesel fuel and empty it again using the Guided Function "Check electric fuel pump".

- Replace the fuel filter. Refer to => [ Fuel Filter ] Fuel Filter.

- Replace the following high pressure components:

• High pressure pump. Refer to => [ High Pressure Fuel Pump ] High Pressure Fuel Pump.

• High pressure lines. Refer to => [ High Pressure Line, Installing ] Service and Repair.

• High pressure fuel rail including the fuel pressure regulator valve (N276) and fuel pressure sensor (G247). Refer to => [ Fuel Rail and Injectors Overview ] Service and Repair.

• Fuel injectors. Refer to => [ Fuel Injector ] Fuel Injector.

• Fuel return lines (overflow oil lines). Refer to => [ Fuel Rail and Injectors Overview ] Service and Repair.

- Connect the fuel return line, which is blue or has a blue mark, - A - to the fuel delivery unit.

- Fill the fuel tank completely with diesel fuel.

- Fill and bleed the fuel system. Refer to => [ Fuel System, Filling and Bleeding ] Fuel System, Filling and Bleeding.

- Perform a road test.