Fuel Pressure, Checking

Fuel Pump, Checking

• When replacing the fuel delivery unit, check the fuel tank for visible contamination and clean if necessary.

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

Fuel Pressure, Checking

Conditions

• The fuel pump function must be checked. Refer to => [ Function and Voltage Supply, Checking ]. Function and Voltage Supply, Checking

Sequence

Read safety precautions before beginning work. Refer to => [ Safety Precautions ] Fuel Supply.

- Observe the rules for cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply.

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 ]. Residual Pressure, Checking

If the Specification is Exceeded

- Pressure relief valve in the flange is malfunctioning, replace the flange with the fuel filter - item 20 -=> [ Flange with Fuel Filter ] Fuel Tank and Components Overview.

If the Specification is Not Obtained:

- Check the fuel lines for possible restrictions (kinks) or blockages.

If no malfunction can be found:

- Replace the flange with the fuel filter and pressure relief valve - item 20 -=> [ Flange with Fuel Filter ] Fuel Tank and Components Overview.

- Repeat the test.

If specified value is again not obtained:

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