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)

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

• Vehicle Diagnostic Tester

• Measuring container, fuel-resistant

Checking the Fuel Pressure

• 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.

- Remove the cap from the fuel filler tube.













Risk of injury from fuel.

• To reduce pressure in the fuel system, lay a clean cloth around the connector and carefully loosen connector.

- Disconnect the fuel line by first folding the boot - 1 - downward.

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

- Remove the hose coupling with the release buttons pressed.

- Connect the (V.A.G 1318) and adapters to the fuel supply hose as illustrated.






- Push an assisting hose - arrow - onto it and hold it into a measuring container.

• It is necessary to first bleed the fuel system before measuring the pressure.

- Connect the vehicle diagnostic tester.

- Select "engine electronics" in On Board Diagnostic (OBD).

- Select "output diagnostic test mode".

- Select "fuel pump electronics" and press "start".

- Close the shut-off valve on the pressure gauge as soon as fuel starts to come out of the auxiliary hose.






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

- 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 specified value is not reached, check the fuel pump delivery rate.

Checking Holding Pressure

- Check for leaks and constant pressure. Watch the (V.A.G 1318) for a drop in pressure while doing this.

• After 10 minutes there must be a residual pressure of at least 3.0 bar.

If residual pressure drops below 3.0 bar:

• Check connection between pressure gauge and fuel line for leaks.

• Check the pressure gauge for leaks.

• Check fuel lines and their connections for leaks.

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

• Replace fuel pump.

Assembling

Assemble in reverse order of disassembling. Note the following:






• 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.