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







- Pressure gauge K-Jetronic V.A.G 1318
- Pressure gauge adapter V.A.G 1318/10-12







- Remote Control V.A.G 1348/3A with adapter cable V.A.G 1348/3-3
- Measuring container, fuel-resistant

Test conditions
- Battery voltage at least 12.5 V.
- Fuel filter OK.
- Fuel tank at least 1/4 filled.
- Fuel Pump (FP) Control Module J538 OK; checking.
- Ignition switched off.

Checking fuel pressure

Sedan with front wheel drive:
- Remove carpeting in luggage compartment.
- Fold forward right backrest of rear seat, if necessary.

Wagon with front wheel drive:
- Remove left 1/3 backrest.
- Remove left side trim in luggage compartment and dirt tray.

All with front wheel drive:
- Fold forward right backrest of rear seat, if necessary.
- Remove luggage compartment floor trim.







- Remove cover for locking flange - arrows -.







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


Vehicles with all wheel drive:
- Remove rear seat bench.







- Remove cover for right locking flange - arrows -.







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

All:







- Connect Remote Control V.A.G 1348/3A with adapter cable V.A.G 1348/3-3 with an adapter cable from Connector Test Set V.A.G 1594C at terminal - 1 -.
- Cover 2nd connector terminal of adapter cable V.A.G 1348/3-3 with insulating tape to prevent short circuit - arrow -.
- Route Remote Control V.A.G 1348/3A switch forward in engine compartment.
- Connect contact - 4 - to vehicle Ground (GND) using a self-made adapter cable.
- Connect alligator clip to battery "+".







- Pull rear engine cover off - arrows -.

CAUTION:
- 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 fuel line - arrow -.







- Connect Fuel Inj. Pressure Gauge-CIS V.A.G 1318 with Adapter V.A.G 1318/11 and V.A.G 1318/12 in fuel line.
- Connect assisting hose - arrow - to pressure gauge and hold it in a measuring container.
- Open shut-off valve of pressure gauge. The lever points in direction of flow.
- Bleed fuel system, by briefly pressing remote control.







- Close shut-off valve of pressure gauge. Lever stands perpendicular to direction of flow - arrow -.
- Hold switch of remote control until no more pressure increase is observed on fuel pressure gauge.
- Specified value: approx. 6 bar positive pressure

If specification is not obtained:
- Check delivery quantity of Fuel Pump (FP).

Checking residual pressure
- Check for leaks and for residual pressure by observing pressure loss on 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 connection between fuel pressure gauge and fuel line for leaks.
- Check pressure gauge for leaks.
- Check fuel lines and their connections for leaks.
- Replace fuel filter with integrated fuel pressure regulator.
- Replace fuel pump.

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

NOTE: Before disconnecting pressure gauge, release pressure by opening shut-off valve. Hold a container in front of connection for this.

Torque specifications
Fuel line to fuel rail 28 Nm