Fuel System Pressure, Pressure Regulator and Holding Pressure, Checking

Fuel System Pressure, Pressure Regulator And Holding Pressure, Checking







NOTE: The fuel pressure regulator regulates the fuel pressure according to the intake manifold pressure. The pressure drop at the injectors remains constant for each engine speed and load range.

Special tools and equipment required
- Pressure gauge V.A.G 1318
- Adapter set V.A.G 1318/17
- Hose clamp pliers V.A.G 1921

Requirements
- Fuel pump relay OK
- Fuel pump OK; checking
- Fuel filter OK
- Battery voltage at least 12.7 V

Checking system pressure
- Briefly open fuel tank filler cap (to release pressure).







- Open cover of use carrier and remove fuse 28 for Fuel pump -G6- (pre-supply pump).

WARNING: The fuel system is under pressure. Place a cloth around the connection point before opening the system. Then carefully loosen the connection to relieve pressure.







- Disconnect fuel supply line -1- by pressing release tab.







- Connect pressure gauge V.A.G 1318 with adapters V.A.G 1318/9 and V.A.G 1318/17 to fuel supply line.
- Open cut-off valve on pressure gauge. Lever must point in direction of flow.
- Reinstall fuse 28 for Transfer Fuel Pump (FP) -G6- (pre-supply pump) in fuse carrier.
- Start engine and run at idling speed.
- Measure fuel pressure

Specification: approx. 3.5 bar







- Disconnect vacuum hose at fuel pressure regulator.

Fuel pressure must increase to approx. 4.0 bar
- Switch off ignition.
- Check for leaks and residual pressure by watching drop in pressure on pressure gauge.

After 10 minutes pressure must still be at least 3.0 bar

If the residual pressure drops below 3.0 bar:
- Start engine and run at idling speed.







- Allow pressure to build up, then switch off ignition. Simultaneously, close cut-off valve of pressure gauge V.A.G 1318 (lever perpendicular to direction of flow - arrow-)
- Observe pressure drop on pressure gauge.

If the pressure now does not drop:
- Check fuel pump non-return valve.

If the pressure drops again:
- Open cut-off valve on pressure gauge (lever points in direction of flow).
- Start engine and run at idling speed.
- Allow pressure to build up, then switch off ignition. Simultaneously, tightly clamp off return hose (with blue marking).

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

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

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