Testing fuel pressure regulator and holding pressure — AUDI

Special tools and workshop equipment required

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 gearbox: Selector lever in P or N position

Note:

The fuel pressure regulator regulates the fuel pressure according to intake manifold pressure.

Warning!
The fuel system is pressurised. 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 pressurised union with a cloth.
Open the union -arrow- and catch escaping fuel with a cloth.
Connect pressure tester V.A.G 1318 with adapters V.A.G 1318/6 and 1318/7 between supply pipe and fuel rail.
Open cut-off valve on pressure gauge (valve handle points in direction of flow).
Start the engine and run at idling 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, fit a new fuel pressure regulator.

The fuel pressure should increase to approx. 4.0 bar.

If specification is not obtained:

Fit a 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 pipe for damage (e.g. pinching) and renew if necessary.

If specification is obtained:

Reconnect vacuum hose.
Switch off the ignition.

Observe pressure drop on pressure gauge to check leakage and holding pressure.

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

If the holding pressure drops below 3.0 bar:

Start the engine and run at idling speed.
Switch ignition off after the pressure has built up. At the same time close cut-off valve on pressure gauge V.A.G 1318 (valve handle at 90° to direction of flow).
Observe pressure drop on gauge.

If the pressure drops again, the following faults are possible:

Unions on pressure gauge downstream of cut-off valve leaking
Fuel pressure regulator defective
Injectors leaking

If the pressure does not drop, the following faults are possible:

Union between pressure gauge and fuel supply pipe leaking
Supply pipe leaking at fuel tank

Non-return valve in fuel pump leaking.

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Fuel supply system - Petrol engines
Fuel supply system