Checking return flow rate of injectors with engine running — AUDI

🧭 Before you start

Fits: Audi Q3 (8U, 2011–2018)

• Special tools named: 3094
• Renewed: affected component

Don't miss

• Risk of malfunctions caused by dirt.Observe Rules for cleanliness. — Seal off open return line connection with plug (1).
• Risk of malfunctions caused by dirt.Observe Rules for cleanliness. — Clean all return line connections (e.g. with commercial cleaning solution etc.) before removing.
• Risk of damage to injectors when return lines are disconnected.Do NOT press the accelerator during this test; the engine must only run at idling speed. — Start engine and let it idle for several minutes.
• When the engine is warm and running at idling speed, the return flow rates at each of the 4 return lines must not differ by more than a small amount (example (1)).
• If one injector has a significantly higher return flow rate than the others (example (2)), it must be renewed .

🔧 Engine codes this applies to

📋 Procedure

1. Remove engine cover panel .
2. Disconnect hose connection (2) at fuel return line.
3. ⚠ Risk of malfunctions caused by dirt.Observe Rules for cleanliness. — Seal off open return line connection with plug (1).
4. Hold end of fuel return hose (2) (lengthen if necessary) in a measuring container to measure the total return flow rate.
5. Start engine and let it idle for 2 minutes.

6. If specification is attained, increase engine speed to 2000 ... 2500 rpm for approx. 2 minutes and then check return flow rate again. [Note: 1000 ml = 1 litre] [Note: Each injector normally has a relatively low return flow rate. If the return flow rate at one injector is relatively high compared to the other injectors, that injector is probably defective.]
7. ⚠ Risk of malfunctions caused by dirt.Observe Rules for cleanliness. — Clean all return line connections (e.g. with commercial cleaning solution etc.) before removing.
8. Dry all components after cleaning.
9. Clamp off fuel return hose (arrow) using hose clamp up to 25 mm 3094.
10. Detach noise insulation.
11. Pull release tabs upwards (arrows) and pull return line connections (1) off injectors.
12. Connect adapters of return flow meterVAS 6684 to return line connections of all 4 injectors.
13. ⚠ Risk of damage to injectors when return lines are disconnected.Do NOT press the accelerator during this test; the engine must only run at idling speed. — Start engine and let it idle for several minutes.
14. When the engine is warm and running at idling speed, the return flow rates at each of the 4 return lines must not differ by more than a small amount (example (1)).
15. If one injector has a significantly higher return flow rate than the others (example (2)), it must be renewed .
16. When the engine is warm and running at idling speed, the return flow rates at each of the 4 return lines must not differ by more than a small amount.
17. Check O-ring for fuel return line connection for damage and deformation. [Note: Lubricate all seals with engine oil or assembly oil before installing.]
18. Push return line connections carefully onto injectors. The catch should engage audibly. Then press release pin down carefully.
19. Erase entry in event memory using .
20. Run engine at idling speed for several minutes (do not press accelerator) and then switch off. Fuel system will bleed itself automatically.
21. Check the entire fuel system for leaks.
22. Renew the affected component if leakage occurs.
23. After completing the repair, road-test the vehicle. Accelerate with full throttle at least once. Then check the high-pressure section of the fuel system again for leaks.
24. Install engine cover panel .

Other AUDI procedures

• Aligning tailpipes · 7 torque figures
• Poly V-belt drive - exploded view · 7 torque figures
• Removing and installing toothed belt for high-pressure pump · 3 torque figures
• Removing and installing exhaust manifold (left-side) – Audi · 4 torque figures
• Removing and installing turbocharger 1 control unit J724 - vehicles with 2.7 ltr. engine from 12.2005 · 3 torque figures
• Removing and installing toothed belt – Audi · 56 torque figures
• Removing engine – Audi A8 D3 · 41 torque figures
• Removing camshaft timing chain from camshafts – Audi A6/A7 C7 · 38 torque figures
• Installing engine – Audi A8 D4 · 36 torque figures
• Removing and installing camshaft timing chain · 29 torque figures