Fuel Pressure and Residual Pressure Before High Pressure Pump, Checking

Fuel Pressure and Residual Pressure before High Pressure Pump, Checking

Special tools, testers and auxiliary items required

• Fuel Inj. Pressure Gauge-CIS (V.A.G 1318)

• Adapter (V.A.G 1318/11)

• Adapter Set (V.A.G 1318/17A)

• Adapter Set (V.A.G 1318/17-1A)

• Fuel Line Feed Adapter (V.A.G 1318/23)

• Measuring container, fuel-resistant

• Protective gloves

Test Conditions

• Battery voltage at least 12.5 V.

• Fuel filter OK.

• Fuel tank at least 1/4 full.

• Fuel Pump (FP) control module (J538) OK; checking

• The ignition is off.

Checking the Fuel Pressure

Before removing pressure gauge, release fuel pressure by opening the shut-off valve. Hold a container under the connection.

• Before opening high pressure components of the fuel injection system, pressure must be relieved to residual pressure. Refer to => [ Releasing Pressure in the High Pressure Area ] Releasing Pressure In the High Pressure Area.

• Wrap a clean cloth around the connection and relieve residual pressure by carefully loosening the connection.

- Disconnect the fuel supply line by first stretching the boot - 1 - downward.

- First push the hose coupling - 2 - downward - arrow A -, then press the release buttons - arrow B -.






- Remove the hose coupling with the release buttons pressed.

- Attach the (V.A.G 1318/23) and (V.A.G 1318/17A) to the (V.A.G 1318).






- Push the (V.A.G 1318/17-1A) onto the disconnected fuel supply line.

- Attach (V.A.G 1318/11) to (V.A.G 1318).

- Place the hose - arrow - in a measuring container.






- Close shut-off valve on (V.A.G 1318).






• Lever stands perpendicular to direction of flow - arrow -.

- Connect the vehicle diagnosis tester.

- Select "engine electronics" in OBD.

- Select "output diagnostic test mode".

- The fuel pump must start running.

• This function controls the fuel pump.

- Read the fuel pressure on the (V.A.G 1318).

• Specified value: Approximately 5 bar (3 to 6 bar) pressure.

- Stop the function when the fuel pressure stops rising on the (V.A.G 1318).

If the specification is not obtained:

- Check the fuel pump delivery rate.

Checking Holding Pressure

- Check for leaks and residual pressure by watching for the pressure on the (V.A.G 1318) to decrease.

• After 10 minutes there must be a residual pressure of at least 3 bar.

If the residual pressure drops below 3 bar:

• Check connection between (V.A.G 1318) and the fuel supply line for leaks.

• Check the (V.A.G 1318) for leaks.

• Check the fuel lines and their connections for leaks.

• Replace fuel filter with integrated fuel pressure regulator. Then repeat test.

• If the fuel filter is OK, replace fuel pump.

Install in reverse order of removal. Note the following:

- The ignition must be off.

• Before removing the pressure gauge, release the fuel pressure by opening shut-off valve. Hold a container - arrow - under the connection.






- Connect the fuel supply line (make sure it is clean).

• Check fuel system for leaks.