With Manufacturer's Scan Tool

Fuel pressure regulator and residual fuel pressure, checking

Requirements
- Fuel pump relay OK
- Fuel pump OK
- Fuel filter OK
- Battery voltage at least 11 V

NOTE: The fuel pressure regulator regulates the fuel pressure according to in take manifold pressure.

WARNING!
Fire hazard! 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 pulling off the hose or cap.


- Briefly open fuel tank filler cap (to release pressure).
- Cover fuel pressurized connection with cloth.







- Open connection -arrow- and catch escaping fuel with cloth.







Connect VAG1318 pressure tester with adapters VAG1318/6 and 1318/7 between fuel supply line and fuel rail.
- Open cut-off valve on pressure tester. Valve handle points in direction of flow.

NOTE: Pressure tester cut-off valve must be open (lever pointing in direction of flow).

- Start engine and run at idle speed.
- Measure fuel pressure.
Specification: approx. 3.5 bar







- Pull vacuum hose -arrow- off fuel pressure regulator.


NOTE: If fuel flows out at the vacuum connection on the fuel pressure regulator during the following pressure test, install a new fuel pressure regulator.

The fuel pressure must increase to approx. 4.0 bar positive pressure.

If specification is not obtained:
- Install new pressure regulator as a trial measure and repeat the pressure test.
If fuel pressure still does not match specification, check fuel pump and supply line for damage (e.g. pinching) and replace if necessary.

If specification is obtained:
- Reconnect vacuum hose.
Switch ignition off.
Observe pressure drop on pressure gauge to check leakage and residual pressure.

After 10 minutes the pressure should still be at least 3 bar.

If holding pressure drops below 3.0 bar:
- Start engine and run at idle speed.







Switch ignition off after pressure has built up. At the same time close cut-off valve on VAG1318 pressure gauge (valve handle at 90 ° to direction of flow).
- Observe pressure drop on gauge.

If the pressure drops again, the following malfunctions are possible:
- Connections on pressure gauge downstream of cut-off valve leaking
- Fuel pressure regulator faulty
- Fuel injectors leaking

If the pressure does not drop, the following malfunctions are possible:
- Connection between pressure gauge and fuel supply line leaking
- Fuel supply line leaking at fuel tank
- Check valve in fuel pump leaking.