Fuel Pressure: Testing and Inspection

Fuel Pressure Regulator and Residual Pressure, Checking

• Fuel pressure regulator is integrated in fuel filter and cannot be replaced individually.

Special tools, testers and auxiliary items required

• Hose Clamps Up to 25 mm Dia. (3094)

• Fuel Inj. Pressure Gauge-Cis (V.A.G 1318) with Adapters (V.A.G 1318/11), (V.A.G 1318/17) and (V.A.G 1318/23)

Procedure

• Fuel Pump (FP) Relay OK.

• Fuel Pump (FP) OK, checking.

• Fuel filter OK.

• Battery voltage min. 12.5 V.

Measuring fuel pressure:





- Press both latches in direction of - arrow - and remove engine compartment E-box cover.

- Remove Fuel Pump (FP) 2 Relay (J49) - 2.1 -.





• Removing the fuel pump (FP) 2 relay (J49) prevents the fuel pump from starting when the driver's door is opened.

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

- Disconnect fuel supply line - arrow - by pulling release ring.





- Disconnect fuel supply line - arrow - from fuel rail.





- Connect (V.A.G 1318) with (V.A.G 1318/11), (V.A.G 1318/17) and (V.A.G 1318/23).





- Connect pressure gauge to fuel supply line.

- Install a fuel-resistant auxiliary hose on fuel rail and on pressure gauge.

• Use hose clamps - arrows - to secure assisting hose.

- Open shut-off valve of pressure gauge set.

• The lever points in the direction of flow.

- Start engine and let run at idle.

- Measure fuel pressure.

• Specified value: approximately 4.0 bar positive pressure

- Switch off ignition.

If the specification is not obtained:

- Check delivery quantity of Fuel Pump (FP).

Checking seal and residual pressure:

- Check for leaks and for residual pressure by observing the pressure loss on the pressure gauge.

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

If the residual pressure drops below 3.0 bar:

- Start engine and let run at idle.

- Wait until pressure has built-up, and then switch off ignition. Simultaneously close shut-off valve of (V.A.G 1318).





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

- Observe pressure drop on pressure gauge.

If the pressure drops again:

- Check line connections, o-rings on fuel rail and injectors for leaks.

- Check pressure gauge for leaks.

If the pressure does not drop:

- Open shut-off valve of pressure gauge (lever in direction of flow).

- Remove rear seat bench.

- Unclip catches - arrows - of right connector flange cover.





- Disconnect fuel return line - arrow - by pressing release button.





- Connect (1318/17-1) to fuel return line.





- Clamp off adapter piece using a (3094).

• (3094) must not be placed directly on fuel line, otherwise it may be damaged.

- Cover return line connection with a cloth.

- Start engine and let run briefly at idle.

- Wait until pressure has built-up, and then switch off ignition.

- Observe pressure drop on pressure gauge.

If pressure does not drop now, check-valve of fuel pump is malfunctioning.

- Replace fuel pump.

If the pressure drops again:

- Replace fuel filter with integrated fuel pressure regulator.

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

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

• Secure all hose connections with hose clamps appropriate for the model.

- Reconnect fuel pump (FP) 2 relay (J49) - 2.1 - to relay and fuse holder.





- Install rear seat bench.