Residual 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)

• Measuring Container, 2 Liter

Residual Pressure, Checking

Conditions

• Fuel pressure OK and the (VAS 6550) is still connected. Checking fuel pressure, refer to => [ Fuel Pressure, Checking ]. Fuel Pressure, Checking





Sequence

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

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

• Target value: 4.0 to 7.0 bar

- Watch the pressure decrease on the (VAS 6550). After 10 minutes the pressure must not drop below a 3.0 bar decrease.

If the pressure drops further:

- Activate the fuel pump with output DTM to build fuel pressure.

- Close the shut off lever - B - on the (VAS 6550) as soon as pressure accumulates. The lever is perpendicular to the direction of flow.





If Pressure no Longer Drops Now

Check for the leak on the engine side. Repeat the residual pressure check. Close the shut off lever - A - this time to determine if there actually is a leak on the engine side.

- Check the fuel pipe to high pressure pump for leaks.

If no malfunction can be found:

- Replace the high pressure pump. Refer to => [ High Pressure Pump ] Two Piece Intake Manifold.

If Pressure Drops Again

Check for the leak on the fuel tank side. Proceed as follows:

- Check the fuel line to the flange for leaks.

If no malfunctions are found with the fuel line:

The pressure relief valve in the flange or pressure retention valve in the fuel pump leaks.

- Replace the flange with the fuel filter and repeat the pressure retention test. If the leak is still present, replace the fuel delivery unit. Refer to one of the following:

Front Wheel Drive (FWD), refer to - item 20 -=> [ Flange with Fuel Filter ] Fuel Tank and Components Overview.

All Wheel Drive (AWD), refer to - item 22 -=> [ Flange with Fuel Filter ] Fuel Tank and Components Overview.