Fuel Pressure Regulator and Residual Pressure, Checking

Fuel Pressure Regulator and Residual Pressure, Checking

Special tools, testers and auxiliary items required

• Fuel injection pressure gauge (VAG 1318)

• Adapter set (VAG 1318/17A)

• The fuel pressure regulator is integrated in the fuel filter and regulates the fuel pressure at approximately 4.0 bar.

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

• Observe the rules for cleanliness. Refer to => [ Clean Working Conditions ] Clean Working Conditions.

Test Sequence

CAUTION!
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 release the pressure by carefully disconnecting the connection.

- Disconnect the fuel supply line - 1 - and collect any leaking fuel with a cloth.





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

- Install the (VAG 1318) with the ( VAG 1318/17A).





- Open the shut off lever on the (VAG 1318).

- Start the engine and run at idle speed.

• If the engine does not start, activate the fuel pump with the output Diagnostic Test Mode (DTM).

- Read the fuel pressure on the (VAG 1318). Specified value: 3.8 to 4.2 bar.

If the fuel pressure is OK, check the retaining pressure, refer to.

If the Specification is Exceeded

- Check the fuel return line between the fuel filter and fuel delivery unit for possible restrictions (kinks) or blockages.

If no malfunction can be found:

- The fuel pressure regulator is faulty. Replace the fuel filter with integrated fuel pressure regulator. Refer to => [ Fuel Filter ] Fuel Filter.

If the Specification is Not Obtained

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

If no malfunction can be found:

- Replace the fuel filter with integrated fuel pressure regulator. Refer to => [ Fuel Filter ] Fuel Filter.

- Repeat the test.

If specified value is again not obtained:

- Fuel pump is faulty, replace fuel delivery unit. Refer to => [ Fuel Delivery Unit ] Fuel Delivery Unit.

If the Specified Value is Not Reached, Check the Residual Pressure

- Switch off the ignition.

- Observe the pressure drop on the (VAG 1318). After 10 minutes, the pressure must not drop below 3.0 bar.

If the residual pressure drops below:

- Start the engine and run at idle speed.

- Switch the ignition off and immediately close the shut off lever on the (VAG 1318). Lever stands perpendicular to direction of flow - arrow -.





If the Pressure Drops Again

(Leak on engine side)

- Check the fuel rail and fuel injectors for leaks.

If the Pressure No Longer Drops

(Leak on fuel tank side)

- Check the fuel lines for leaks.

If no malfunctions are found in the fuel lines:

- Test the fuel pump check valve. Refer to => [ Fuel Pump, Checking ] Testing and Inspection.

If no malfunction is found here either:

- Replace the fuel filter with integrated fuel pressure regulator. Refer to => [ Fuel Filter ] Fuel Filter.

When removing the (VAG 1318) after completing the test

- Switch off the ignition.

- Open the shut off lever on the (VAG 1318) set.

CAUTION!
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 release the pressure by carefully disconnecting the connection.

- Remove the (VAG 1318) with adapters.