Fuel Pressure Regulator and Holding Pressure, Checking

Fuel Pressure Regulator And Holding Pressure, Checking

NOTE: The fuel pressure regulator is found in the fuel filter under the tank.







Special tools and equipment
- V.A.G 1318 with V.A.G 1318/6 and V.A.G 1318/7

Test conditions
- Fuel pump relay OK
- Fuel pump OK Fuel filter OK
- Battery voltage at least 11 V
- Vehicles with automatic transmission: Selector lever set to P or N

Check pressure system
- Open the fuel tank lid briefly (pressure should drop).
- Remove engine cover.

CAUTION: The fuel system is pressurized. Before loosening hose connections or opening the test connection (to measure fuel pressure), place a cloth around the connection. Then release pressure by carefully loosening the connection.

- Use cloth to cover union (subject to fuel pressure).







- Remove fuel hose from fuel rail pipe connection.. To do so, counterhold using an open end wrench at each hex head -1- and -3- and remove union nut -2-.
- Unscrew pressure gauge V.A.G 1318 with adapters V.A.G 1318/6, 1318/7 between supply line and fuel rail.
- Open pressure gauge cut-off valve. Lever points in direction of flow.
- Start engine and run at idling speed.
- Measure fuel pressure.
Specification: approx. 3.5 bar
- Switch ignition off.
- Test for leaks and holding pressure by watching pressure drop on gauge.
- After 10 minutes the remaining pressure should be at least 2.5 bar.

If holding pressure drops below 2.5 bar:
- Start engine and run at idling speed.







- Switch off ignition once pressure has built up. At the same time, close cut-off valve of pressure gauge V.A.G 1318 (lever at right angle to direction of flow).
- Observe pressure drop on gauge.

Pressure drops again:
- Check pressure gauge for tightness.
- Check line and O-rings at the fuel rail and injectors for tightness.

Pressure does not drop:
- Check pressure regulator in fuel filter


Vehicle with all-wheel drive:
- Remove rear seat







- Remove locking flange cover and screws (arrows).







- Remove fuel return line (arrow) from locking flange (left vehicle side).







- Attach adapter V.A.G. 1318/17 1 on return line.
- Use hose clamp 3094 to clamp adapter V.A.G. 1318/17 1.

NOTE: The hose clamp 3094 may not set directly on the fuel line - danger of damage.

- Start engine and run at idling speed.







- Switch ignition off once pressure has built up. At the same time, close cut-off valve of pressure gauge V.A.G 1318 (lever at right angle to direction of flow).
- Observe pressure drop on gauge.

Pressure drops again:
- If valve is defective, replace fuel pump (check valve defective).

The pressure does not drop:
- Replace fuel filter

The pressure drops again:
- Check pressure gauge for tightness.

NOTE:
- Before removing the pressure gauge, lower fuel pressure by opening the shut-off valve. Hold container at the connection.
- The assembly of the fuel system is in reverse order of removal.







- 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.
- Bleed air from fuel system

Bleed air from fuel system
- Start engine, run it at the middle rpm range for several minutes, and then turn ignition off again.

NOTE: The engine may run rough at the beginning because of air in the fuel system.

- Examine fuel system for leakage.
- Check DTC memory, if necessary delete.
See Vehicle diagnostic, testing and information system VAS 5051

- Consider the safety precautions valid for a test drive.

- Perform a test drive with at least one full load acceleration, after which the fuel system is to be inspected for leaks again.
- After the test drive check the DTC memory again. If a DTC is present again, erase the memory and generate a new readiness code.
- Read readiness code if no DTC is stored. If readiness code is not OK, generate a new one.