Audi Workshop Service and Repair Manuals

Test conditions

• ● Fuel pump relay OK; testing .
• ● Fuel pump OK
• ● Fuel filter OK
• ● Battery voltage OK.

Note:

The fuel pressure regulator regulates the fuel pressure according to the intake manifold pressure at the throttle valve unit.

• ‒ 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 gauge V.A.G 1318 into fuel supply pipe using adapters 1318/7 and 1318/15.
• ‒ → 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 must increase to approx. 4.0 bar.

If specification is not obtained:

• ‒ Replace the fuel 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 ignition.
• ‒ Observe pressure drop on gauge.

• After 10 minutes the remaining pressure should be at least 2.5 bar.

If the holding pressure drops below 2.5 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 (lever at 90° to throughflow direction).
• ‒ Observe pressure drop on gauge.

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

• ◆ Fuel pressure regulator defective
• ◆ Injectors leaking
• ◆ Unions on pressure gauge downstream of cut-off valve 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
• ◆ Return valve in fuel pump leaking

=> 4-cylinder Engine, Mechanics; Repair Group 20; Removing and installing fuel pump