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

• If there are concerns about driving behavior, the fuel pressure can be checked during a road test. Refer to => [ Fuel Pressure, Checking while Driving ]. Fuel Pressure, Checking While Driving


The fuel supply line is under pressure! Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before disconnecting the connection, wrap a cloth around the connection. Then, disconnect the connection carefully to release the pressure.

- Disconnect the supply line (metal coupling) - arrow - and collect the 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 the 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 ]. Residual Pressure, Checking

If the Specification is Exceeded:

- Check the return line between the fuel filter and fuel pump (FP) for kinks and blockage.

If No Malfunction can be Found:

- Pressure relief valve in the fuel filter is malfunctioning, replace 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 minimum of 7.0 bar. If 7.0 bar is reached, open the shut-off valve again immediately!





If the Pressure has Increased:

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

If the Pressure does not Increase:

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