Checking fuel pressure regulator and residual pressure (engine code letters BHT) — AUDI

🧭 Before you start

Fits: Audi A8 D3 (4E, 2002–2010)

• Special tools named: V.A.G 1318, V.A.G 1318/15
• Renewed: if necessary

Don't miss

• The union is located behind the cylinder head of cylinder bank 1 (cylinders 1 to 6), under the black plastic cover.
• Cut-off valve on pressure gauge must be open (lever pointing in direction of flow).
• If fuel flows out at the vacuum connection on the fuel pressure regulator during the following pressure test, fit a new fuel pressure regulator.
• Whether or not a pressure drop is indicated on the pressure gauge depends on which direction the cut-off valve on the pressure gauge is pointing in (towards fuel tank or intake manifold).
• Before removing the pressure gauge, release the fuel pressure by opening the cut-off valve. Hold a container under the connection.

🔧 Engine codes this applies to

📋 Procedure

1. ⚠ 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 unscrewing the connection. — Briefly open fuel tank filler cap (to release pressure).
2. Cover pressurised union with a cloth.
3. Open the union and catch escaping fuel with a cloth. [Note: The union is located behind the cylinder head of cylinder bank 1 (cylinders 1 to 6), under the black plastic cover.]
4. Connect pressure gauge V.A.G 1318 with adapters V.A.G 1318/15, 1318/7 between supply line and fuel rail.
5. Open cut-off valve on pressure gauge. The lever points in the direction of flow. [Note: Cut-off valve on pressure gauge must be open (lever pointing in direction of flow).]

6. Start the engine and run at idling speed.
7. Measure the fuel pressure.
8. 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.]
9. Fit a new pressure regulator as a trial measure and repeat the pressure test.
10. If fuel pressure still does not match specification, check fuel pump and supply line for damage (e.g. pinching) and renew if necessary.
11. Reconnect vacuum hose.
12. Switch off ignition.
13. Observe pressure drop on pressure gauge to check leakage and residual pressure.
14. Start the engine and run at idling speed.
15. Allow pressure to build up, then switch off ignition. At the same time close cut-off valve on pressure gauge V.A.G 1318 (lever at right angle to direction of flow).
16. Observe pressure drop on pressure gauge. [Note: Whether or not a pressure drop is indicated on the pressure gauge depends on which direction the cut-off valve on the pressure gauge is pointing in (towards fuel tank or intake manifold).]
17. Non-return valve in fuel pump leaking. Fuel supply system, petrol engines; Repair group 20; Fuel supply system [Note: Before removing the pressure gauge, release the fuel pressure by opening the cut-off valve. Hold a container under the connection.]

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