With Manufacturer's Scan Tool

System Pressure, Fuel Pressure Regulator And Residual Pressure, Checking

NOTE:
- The fuel pressure regulator is located in the fuel filter underneath the tank.
- Fuel pressure regulator regulates fuel pressure according to intake manifold pressure. This ensures that the pressure drop at the fuel injectors remains the same for each speed and load range of the engine.

Special tools and workshop equipment required

- V.A.G 1318 Pressure gauge.
- V.A.G 1318/6 Adapter.
- V.A.G 1318/7 Adapter.

Test requirements:

- Fuel pump relay OK.
- Fuel pump OK; checking.
- Fuel filter OK
- Battery voltage at least 12.7 V
- Vehicles with automatic transmission: Selector lever in position P or N.

Checking system pressure

- Remove engine cover -arrows-.
- Open fuel filler flap and briefly open the fuel tank filler cap (to release pressure).
- Remove engine cover.

WARNING: The fuel system is pressurized. Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.

- Open screw connection -1- and collect escaping fuel using a cloth.
- Connect pressure gauge V.A.G 1318 using adapters 1318/6 and 1318/7 to feed line.

- Open shut-off valve of pressure gauge. Lever points in direction of flow.
- Start engine and run at idle.
- Measure fuel pressure.
- Specified value: approx. 4.0 bar excess pressure.
- Switch ignition off.
- Check leak tightness and holding pressure by watching gauge indicator fall.
- After 10 minutes the remaining pressure should be at least 2.5 bar excess pressure.

If the holding pressure drops below 2.5 bar:
- Start engine and run at idle.

- Allow pressure to build up, then switch off ignition. At same time close shut-off valve on pressure gauge V.A.G 1318 (valve lever at right angles to direction of flow -arrow-).
- Observe pressure drop on gauge.

If the pressure drops again:
- Check pressure gauge for leaks.
- Check line connections, O-rings on fuel rail and injectors for leaks.

If the pressure does not drop:
- Check pressure regulator in fuel filter.

Checking fuel pressure regulator - vehicles with front-wheel drive:

- Remove trim in luggage compartment.
- If necessary fold right backrest of rear seat bench forward.

- Unscrew cover for sealing flange -arrow-.

- Disconnect fuel return line -2- from sealing flange.

- Attach adapter piece V.A.G 1318/17 -1 to return line.
- Disconnect adapter piece using hose clamp 3094.

NOTE: Do not attach hose clamp 3094 directly to fuel line. Danger of damage may occur.

- Start engine and run at idling speed.

- Allow pressure to build up, then switch off ignition. At same time close cut off valve on pressure gauge V.A.G 1318 (valve lever at right angles to direction of flow -arrow-).
- Observe pressure drop on pressure gauge.

If the pressure drops again:
- Check fuel pump non return valve.

If the pressure now does not drop:
- Replace fuel filter.

NOTE:
- Before removing the pressure gauge, release the fuel pressure by opening the cut off valve. When doing this hold a container over the connection.
- Assemble the fuel supply in reverse order.

Checking fuel pressure regulator - vehicles with all wheel drive:

- Remove rear bench seat.

- Unscrew cover for sealing flange from left -arrows-.

- Disconnect fuel return line -arrow-from sealing flange (left side of vehicle).

- Attach adapter piece V.A.G 1318/17-1 to return line.
- Disconnect adapter piece using hose clamp 3094.

NOTE: Do not attach hose clamp 3094 directly to fuel line - Danger of damage.

- Start engine and run at idling speed.