Fuel Delivery and Air Induction: Description and Operation

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.

• This information guides the reader through the individual procedures like a flowchart.

• The coupling must audibly engage when locking.

• Note the color code when installing the couplings. Refer to => [ Coupling Allocation: ] Coupling, Disconnecting!

• Pull on the coupling to make sure it is secure.

• Disconnecting the coupling. Refer to => [ Coupling, Disconnecting ] Coupling, Disconnecting.

Was the engine started with the incorrect fuel?

Yes, refer to => [ Step 1 (Engine Was Started with Incorrect Fuel) ].

No, refer to => [ Step 2 (Engine Was Not Started with Incorrect Fuel) ].

Step 1 (Engine Was Started with Incorrect Fuel)

- Drain 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 flange cover.

• Press the lock ring to unlock the fuel line.

If the battery is connected, make sure that the fuel pump is not activated when the door is opened. Fuel may leak out when the system is open.

- Disconnect the fuel return line, which is blue or has a blue mark, - 1 - from the fuel delivery unit. Disconnecting the coupling. Refer to => [ Coupling, Disconnecting ] Coupling, Disconnecting.

- Connect the hose (VAS 6551/5-2) from the pressure tester to the fuel return line - 1 -.

- Place the free end of the hose (VAS 6551/5-2) into a container.

- Connect the vehicle diagnostic tester and perform the guided function "Activate Fuel Pump (evacuate the fuel system)".

• The fuel pump is now activated.

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

Remove the fuel delivery unit, refer to => [ Fuel Delivery Unit ] Fuel Delivery Unit.

- Check the fuel tank for particles.

- Empty the fuel delivery unit reservoir.

- Check the reservoir visually for large contaminants and particles and on the screen.

Are there any particles?

Yes, refer to => [ Step 3 (Particles in the Fuel Delivery Unit and Reservoir) ]

No, refer to => [ Step 4 (No Particles in the Fuel Delivery Unit and Reservoir) ]

Step 2 (Engine Was Not Started with Incorrect Fuel)

- Drain 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.

- Fold the carpet to the side or forward, as necessary.

- Remove the flange cover.

• Press the lock ring to unlock the fuel line.

If the battery is connected, make sure that the fuel pump is not activated when the door is opened. Fuel may leak out when the system is open.

- Disconnect the fuel return line, which is blue or has a blue mark - 1 - from the fuel delivery unit. Disconnecting the coupling. Refer to => [ Coupling, Disconnecting ] Coupling, Disconnecting.

- Replace the fuel filter.

- Fuel the vehicle and perform a road test.

End

Step 3 (Particles in the Fuel Delivery Unit and Reservoir)

- Clean the fuel delivery unit and fuel tank using the suction pump (VAS 5226).

Install the fuel delivery unit, refer to => [ Fuel Delivery Unit ] Fuel Delivery Unit.

- Fill the fuel tank with 5 liters of diesel fuel.

- Drain the fuel tank completely as described above.

- Replace the following high pressure components:

• High pressure pump.

• High pressure lines.

• Fuel rail, including the fuel pressure regulator valve and the fuel pressure sensor.

• Fuel injectors

• Fuel return lines (overflow oil lines).

• Replace the fuel filter.

- Fuel the vehicle.

- Bleed the fuel system.

- Perform a road test.

End

Step 4 (No Particles in the Fuel Delivery Unit and Reservoir)

- Fill the fuel tank with 5 liters of diesel fuel.

- Drain the fuel tank completely as described above.

Removing the fuel metering valve increases the risk that the high pressure pump will be damaged from the outside by debris. For this reason, always make sure that it is clean.

- Carefully clean the high pressure pump near the fuel metering valve.

- Disconnect the connector from the valve.

- Remove the bolts - arrows - and carefully remove the fuel metering valve - A -.

- Inspect the fuel metering valve and the high pressure pump for metal particles.

Are there any particles?

Yes, refer to => [ Step 5 (Particles in the High Pressure Pump) ].

No, refer to => [ Step 6 (No Particles in the High Pressure Pump) ].

Step 5 (Particles in the High Pressure Pump)

- Replace the following high pressure components:

• High pressure pump

• High pressure lines

• Fuel rail, including the fuel pressure regulator valve and fuel pressure sensor.

• Fuel injectors

• Fuel return lines (overflow oil lines).

• Replace the fuel filter.

- Fuel the vehicle.

- Bleed the fuel system.

- Perform a road test.

End

Step 6 (No Particles in the High Pressure Pump)

Make sure that the fuel metering valve seal is not damaged. The high pressure pump must be replaced if the seal is damaged.

- Coat the lower seal for the fuel metering valve with fuel.

- Slide the valve - A - into the high pressure pump by lightly twisting it.

- Install both bolts - arrows - by hand.

- First, tighten the bolts to 3 Nm and then tighten them to 7 Nm.

- Replace the fuel filter.

- Bleed the fuel system.

- Fuel the vehicle and perform a road test.

End