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 Injection Pressure Gauge Set V.A.G. 1318 with Adapter V.A.G. 1318/6 and Adapter V.A.G. 1318/7.







- Remote control V.A.G 1348/3 A with adapter cable V.A.G 1348/3-3

Test requirements
- Fuel Pump (FP) Control Module J538 OK; check.
- The fuel filter OK.
- The parking brake engaged.
- Battery voltage at least 12.5 V.
- The selector lever of automatic transmission in position "P" or "N".
- All electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
- The fuel tank at least 1 / 4 filled.
- The ignition switched off.

Checking system pressure
- Remove the rear seat bench.







- Remove the cover for the right locking flange - arrows -.







- Carefully release and disconnect the electrical harness connector - arrow - at the locking flange.







- Connect the remote control connection V.A.G 1348/3 A with connection V.A.G 1348/3-3 to contact - 5 - using an adapter cable from the connector test set V.A.G 1594 C.
- Using insulating tape, tape over the second contact of connection V.A.G 1348/3-3 to prevent a short circuit - arrow -.
- Route the switch of the remote control V.A.G 1348/3 A forward into the engine compartment.
- Connect the alligator clip to ground (GND) point in the engine compartment.
- Connect the contact - 1 - to battery positive terminal (B+) using a self-made adapter cable.

NOTE: For safety reasons, install a fuse - A - in the cable.







- Remove engine cover - arrows - .

CAUTION: The fuel system is under high pressure! Before opening high pressure components of the fuel injection system, pressure must be relieved to residual pressure . Then wrap a clean rag around the connection and relieve residual pressure by carefully loosening the connection.







- Disconnect the fuel line - arrow - .







- Connect the pressure gauge V.A.G 1318 to the fuel line using adapter V.A.G 1318/11 and V.A.G 1318/12.
- Connect the extension hose - arrow - to the pressure gauge and hold it in a measuring container.
- Open the pressure gauge shut-off valve. The lever points in direction of flow.
- Bleed the fuel system, by briefly pressing the remote control.







- Close the pressure gauge shut-off valve. The lever is perpendicular to the direction of flow - arrow -.
- Hold the remote control switch until no more pressure increase is observed on the fuel pressure gauge.
- Specification: approx. 6 bar positive pressure

If the specification is not obtained:
- Check the delivery rate of the fuel pump.

Checking residual pressure
- Check for leaks and residual pressure by observing the pressure loss on the pressure gauge.
- After 10 minutes there must be a residual pressure of at least 3.75 bar.

The holding pressure drops below 3.75 bar:
- Check the connection between the fuel pressure gauge and the fuel line for leaks.
- Check the pressure gauge for leaks.
- Check the fuel lines and their connections for leaks.
- Replace the fuel filter with integrated fuel pressure regulator.
- Replace the fuel pump.

Assembly is performed in the reverse order of removal. Note the following:

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

Torque specifications
Fuel line to fuel rail 22 Nm