Fuel Pressure Regulator, Checking System Pressure and Residual Pressure
Fuel Pressure Regulator, Checking System Pressure and Residual Pressure
• 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, testers and auxiliary items required
• Pressure gauge (VAG1318)
• Adapter (VAG1318/6)
• Adapter (VAG1318/7)
Requirements
• Fuel pump relay OK.
• Fuel pump OK; checking. Refer to => Fuel Delivery and Air Induction Fuel Delivery and Air Induction
• 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.
Vehicles up to 06.03
CAUTION!
The fuel system is pressurized! Before opening the system place a cloth around the connection. Then release pressure by carefully loosening the connection.
- Disconnect fuel supply line - 1 - and expose.
• Disregard item no. - 2 -.
Vehicles as of 07.03
CAUTION!
Fuel system is under pressure! Before opening system, place rags around the connection point. Then release pressure by carefully loosening connection.
- Unscrew fuel hose from connection on fuel rail pipe. To do so, counterhold using an open-end wrench at each hex head - 1 - and - 3 - and unscrew union nut - 2 -.
Continuation for all vehicles
- Connect pressure gauge (VAG1318) using adapters (VAG1318/6) 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 (VAG1318) (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 (VAG1318/17) -1 to return line.
- Disconnect adapter piece using hose clamp (3094 ).
• 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 (VAG1318) (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.
• 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.
Vehicles up to 06.03
- Tighten union nut for fuel supply line - 1 - to 22 Nm.
Vehicles as of 07.03
- Secure fuel hose to connection on fuel rail pipe. To do so, counterhold using an open-end wrench at each hex head - 1 - and - 3 - and tighten union nut - 2 - to 22 Nm.
Checking fuel pressure regulator - vehicles with all wheel drive
- Remove rear bench seat.
- Remove cover for sealing flange from left (arrows).
- Disconnect fuel return line (arrow) from sealing flange (left side of vehicle).
- Attach adapter piece (VAG1318/17-1) to return line.
- Disconnect adapter piece using hose clamp (3094 ).
• Do not attach hose clamp (3094) directly to fuel line - Danger of damage
- 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 (VAG1318) (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.
Assembly is performed in the reverse order, note the following while doing so:
• Before removing the pressure gauge, release the fuel pressure by opening the cut off valve. When doing this hold a container over the connection.
Vehicles up to 06.03
- Tighten union nut for fuel supply line - 1 - to 22 Nm.
Vehicles as of 07.03
- Secure fuel hose to connection on fuel rail pipe. To do so, counterhold using an open-end wrench at each hex head - 1 - and - 3 - and tighten union nut - 2 - to 22 Nm.