Checking fuel pump delivery rate: Audi A8 D3 (AEH, AGN, AGU, AJQ, …)

🧭 Before you start

Fits: Audi A8 D3 (4E, 2002–2010)

• Renewed: relevant fuel delivery unit

Don't miss

• Disregard (item 1).
• Voltage at fuel pump with engine stationary and pump running is approx. 2 volts less than battery voltage.

🔧 Engine codes this applies to

📋 Procedure

1. Observe test conditions .
2. If fitted, remove cover for suspension turret (right-side); to do so, detach spreader clips (1) and unscrew bolted joint (2).
3. Pull cover out of retainers (arrows).
4. ⚠ Rules for cleanliness when working on the injection system . — Disconnect fuel supply line (2) going to engine at fuel filter. [Note: Disregard (item 1).]
5. Fit auxiliary hose (arrow) onto connection at fuel filter and hold it into a measuring container to catch fuel.

6. Remove luggage compartment side trim cover (right-side) (arrows).
7. Disconnect fuel pump relay J17 located at position (3) on relay and fuse holder in luggage compartment (right-side).
8. Connect remote controlV.A.G 1348/3 A with adapter cableV.A.G 1348/3-2 to contact 2 (arrow) in fuel pump relay socket.
9. Connect crocodile clip of remote controlV.A.G 1348/3 A to vehicle battery "“+”" (positive).
10. Press remote control button for 15 seconds.
11. Compare amount of fuel delivered with minimum delivery shown in diagram (cm3/15 sec.). [Note: Voltage at fuel pump with engine stationary and pump running is approx. 2 volts less than battery voltage.] [Note: As there is hardly any difference in the delivery rate if only one of the two fuel pumps is working – because of the hose connections inside the tank – it is difficult to diagnose a defective pump by just measuring the delivery rate.]
12. Unplug electrical connector for fuel delivery unit (left-side).
13. Measure delivery rate.
14. Unplug electrical connector for fuel delivery unit (right-side).
15. Measure delivery rate.
16. If delivery rate differs considerably from specification, renew relevant fuel delivery unit.

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