Audi Workshop Service and Repair Manuals

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 set to P or N

Note:

The fuel pressure regulator controls the fuel pressure as a function of intake manifold pressure.

• ‒ Briefly open tank cap (pressure dissipation).

• ‒ Use cloth to cover union (subject to fuel pressure).
• ‒ → Unfasten union -arrow- and use cloth to catch fuel emerging.
• ‒ Fit pressure gauge V.A.G 1318 with adapters V.A.G 1318/6, 1318/7 between supply pipe and fuel rail.
• ‒ Open pressure gauge cut-off valve. Lever points in direction of flow.
• ‒ Start engine and let it idle.

• ‒ Measure fuel pressure.

Specification: approx. 3.5 bar

• ‒ → Disconnect vacuum hose -arrow- from fuel pressure regulator.

Note:

Replace pressure regulator if fuel emerges at vacuum connection of pressure regulator when performing the following pressure test.

Fuel pressure must increase to approx. 4.0 bar.

If reading does not match specification:

• ‒ Try replacing pressure regulator and repeat pressure test.
• ‒ If reading still does not match specification, check fuel pump/supply pipe for damage (e.g. crushing) and replace if necessary.

If reading matches specification:

• ‒ Reconnect vacuum hose.
• ‒ Switch off ignition.

• ‒ Check freedom from leaks and holding pressure by way of pressure drop on pressure gauge.

After 10 minutes pressure must still be at least 3 bar.

If holding pressure drops below 3.0 bar:

• ‒ Start engine and let it idle.
• ‒ → 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 angles to direction of flow).
• ‒ Observe pressure drop on gauge.

Possible faults if pressure decreases again:

• ◆ Leak in pressure gauge unions downstream of cut-off valve
• ◆ Fuel pressure regulator defective
• ◆ Injectors leaking

Possible faults if pressure does not decrease:

• ◆ Leak in screw connection between pressure gauge and fuel supply pipe
• ◆ Leak in supply pipe at fuel tank

• ‒ Non-return valve in fuel pump leaking

=> Fuel supply system - petrol engine; Repair Group 20; Fuel supply