Fuel Pressure, Checking

Fuel Pump, Checking

Special tools, testers and auxiliary items required

• Pressure Tester (VAS 6550)

• Remote Control (V.A.G 1348/3A)

• Test Instrument Adapter/DSO (5-pin) (VAS 5565)

• Multi-meter (V.A.G 1715)

• Wrench (T10202)

• Torque Wrench (40-200 Nm) (V.A.G 1332)

• Measuring Container, 2 Liter

Fuel Pressure, Checking

CAUTION!
The fuel system is under pressure!

• Wear protective goggles and protective clothing to prevent injuries and contact with skin.

• Before disconnecting the connection, place a cloth around the connection point. Then release pressure by carefully disconnecting the connection.

- Disconnect the supply line (metal coupling) - arrow - and collect any leaking fuel in a cloth.





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

- Connect the (VAS 6550) to the fuel supply line using (VAS 6550/1) and (VAS 6550/2).





- Make sure the drain is closed and the shut off valves are open.

- Activate the fuel pump with output Diagnostic Test Mode (DTM) to build fuel pressure.

- Check the fuel pressure on the (VAS 6550).

• Specified value: 4.0 to 7.0 bar.

If the fuel pressure is OK, check the residual pressure. Refer to => [ Residual Pressure, Checking ].

If The Specification is Exceeded

- Check the return line between the fuel filter and fuel pump for kinks and/or blockages.

If no malfunction can be found:

- Pressure relief valve in the fuel filter is malfunctioning, replace the fuel filter.

If The Specification is Not Obtained

- Check the fuel pressure before the fuel filter as follows:

- Disconnect the fuel supply line - arrow - from the fuel filter.





- Connect the (VAS 6550) between the fuel filter and fuel supply line using (VAS 6550/1) and (VAS 6550/2).





- Make sure the drain is closed and the shut off valves are open.

- Start the engine and run at idle speed.

- Slowly close the shut off valve - A -. Pressure must increase to a min. 7.0 bar. If 7.0 bar is reached, open the shut off valve again immediately!





If pressure has increased:

- Replace the fuel filter if the fuel pump is OK but the pressure relief valve in the fuel filter is faulty.

If pressure does not increase:

- Replace the fuel delivery unit if the fuel pump is faulty. Refer to => [ Fuel Delivery Unit ] Fuel System Components.