Fuel Holding Pressure, Checking With High Pressure Pump

Fuel Holding Pressure, Checking with High Pressure Pump

Special tools, testers and auxiliary items required

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

• Adapter (V.A.G 1318/11)

• Adapter (V.A.G 1318/17-1)

• 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 minimum 1/4 full.

• Fuel Pump (FP) control module (J538) OK.

• The ignition is off.

Checking the Fuel Pressure

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

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

- Pull the release ring - 1 - and disconnect the fuel line - 2 -.






- Attach (V.A.G 1318/23) and (V.A.G 1318/17-1) to (V.A.G 1318).






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

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

- Connect assisting hose - arrow - on pressure gauge and hold it in a container.

- Close shut-off valve on (V.A.G 1318). Lever stands perpendicular to direction of flow - arrow -.






- Connect a vehicle diagnosis tester.

- Select "Engine electronics" in OBD.

- Select "Output diagnostic test mode".

- 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: Approximately 5 bar (3 to 6 bar) pressure.

If the specification is not obtained:

- Check 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 fuel supply line for leaks.

• Check the (V.A.G 1318) for leaks.

• Check fuel lines and their connections for leaks.

• Check the fuel pump delivery quantity.

• Replace fuel filter with integrated fuel pressure regulator.

• 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 fuel pressure by opening the shut-off valve. Hold a container under the connection.

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






• Check fuel system for leaks.