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)

• Measuring container, fuel-resistant

• Protective gloves

Fuel Pressure, Checking

• Battery voltage at least 12.5 Volts.

• Fuel filter OK.

• Fuel tank at least 1/4 filled.

• Fuel pump control module (J538) OK

• Ignition switched off.

Fuel system is under pressure! Before opening system, place clean rags around the connection. Then release pressure by carefully loosening the connection.

- Push back the boot and disconnect the fuel line - 1 -.





- 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.

- Connect the (V.A.G 1318) to the fuel line with a suitable adapter.





- Attach an assisting hose on (V.A.G 1318) and hold it in a container.

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





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

- Connect the vehicle diagnosis tester.

- Select engine electronics in OBD.

- Then select output diagnostic test.

- Select fuel pump electronics and press start.

• This function controls the fuel pump.

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

• Specified value: 5 to 8 bar

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

If the specification is not obtained:

- Check the fuel delivery quantity of individual fuel pumps.

Residual Pressure, Checking

- 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 fuel pressure gauge and fuel line for leaks.

• Check pressure gauge for leaks.

• Check fuel lines and their connections for leaks.

• Check the fuel delivery quantity of individual fuel pumps.

• Replace the fuel filter with the integrated fuel pressure regulator.

• Check valve in one of the two fuel pumps is faulty.

Assembly is in reverse order of removal, note the following:

- Switch off ignition.

• Before disconnecting pressure gauge, release pressure by opening shut-off valve. Hold the hose in a measuring container - arrow -.

- Connect the fuel supply line 1. Check for cleanliness and leaks.

• Check fuel system for leaks.