Checking holding pressure: VW Polo 6C (AUA, AUB, AXX, AXZ, …)

🧭 Before you start

Fits: VW Polo 6C (2014–2017); platform code 614

• Opens: fuel
• Special tools named: VAS 6550/2
• Renewed: fuel delivery unit

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• Ensure plug-in connectors are secured properly by pulling.
• Ensure that drain tap (C) on pressure tester(1) is closed.
• The fuel pump is now actuated to build up fuel pressure.If the final control diagnosis is to be carried out several times in succession, it may be necessary to start the engine briefly before repeating the final control diagnosis.
• Observe pressure drop on pressure gauge. After 10 minutes, the pressure must not drop by more than 1.0 bar.
• Search for leak on engine side. Repeat holding pressure check. This time, close shut-off tap (A) to check whether leak actually is on engine side.

🔧 Engine codes this applies to

📐 41 workshop diagrams for AUA

Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.

📋 Procedure

1. Observe safety precautions .
2. Observe rules for cleanliness .
3. Pull off supply line (1). Separate plug-in connectors .
4. ⚠ The fuel line is under pressure.Risk of injury to eyes and skin from fuel.Wear eye protection and protective clothing to avoid eye injuries and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully opening the connection point. — Collect escaping fuel with a cleaning cloth.
5. Connect hoseVAS 6550/1 between fuel line to engine and shut-off tap (B).

6. Connect hoseVAS 6550/2 between fuel line from fuel tank and shut-off tap (A).
7. Ensure plug-in connectors are secured properly by pulling.
8. Ensure that drain tap (C) on pressure tester(1) is closed.
9. Shut-off taps (A) and (B) are open.
10. Connect vehicle diagnostic tester.
11. Select final control diagnosis for fuel pump in vehicle self-diagnosis program. [Note: The fuel pump is now actuated to build up fuel pressure.If the final control diagnosis is to be carried out several times in succession, it may be necessary to start the engine briefly before repeating the final control diagnosis.]
12. Read off fuel pressure on pressure gauge.
13. End self-diagnosis, and switch off ignition.
14. Observe pressure drop on pressure gauge. After 10 minutes, the pressure must not drop by more than 1.0 bar.
15. Check all fuel lines for leaks and damage.
16. Actuate fuel pump with final control diagnosis to build up fuel pressure.
17. After pressure has built up, close shut-off tap (B) of pressure tester immediately. Lever is then at right angle to direction of flow. [Note: Search for leak on engine side. Repeat holding pressure check. This time, close shut-off tap (A) to check whether leak actually is on engine side.]
18. If there is a leak on engine side, carry out external check of fuel pipes and high-pressure pump for leaks.
19. Remove spark plugs.
20. Open shut-off valves (A) and (B). Actuate fuel pump with final control diagnosis.
21. Check through spark plug holes whether fuel has collected on piston crown due to a leaking injector.
22. Pull fuel supply line (arrow) off fuel filter. Separate plug-in connectors .
23. ⚠ The fuel line is under pressure.Risk of injury to eyes and skin from fuel.Wear eye protection and protective clothing to avoid eye injuries and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully opening the connection point. — Collect escaping fuel with a cleaning cloth.
24. Connect pressure testerVAS 6550 between fuel filter and fuel supply line using hoseVAS 6550/1 and VAS 6550/2.
25. Connect hoseVAS 6550/1 to fuel line leading to fuel tank.
26. Connect hoseVAS 6550/2 to connection (A) of pressure testerVAS 6550.
27. Use hoseVAS 6550/2 to connect fuel filter to pressure testerVAS 6550.
28. Ensure plug-in connectors are secured properly by pulling.
29. Ensure that drain tap (C) on pressure testerVAS 6550(1) is closed.
30. Shut-off taps (A) and (B) on pressure testerVAS 6550(1) must be open.
31. Repeat Final control diagnosis to build up fuel pressure.
32. After pressure has built up, close shut-off tap (A) of pressure tester immediately. Lever is then at right angle to direction of flow.
33. Observe pressure drop on pressure gauge.
34. Check fuel line for leaks and damage.
35. Check fuel filter for leaks and damage.
36. Proceed as follows to check residual pressure on fuel delivery unit:
37. Fold up bench seat General body repairs, interior72Rear seats; Removing and installing bench seat/individual seats.
38. If fitted, unclip fuel pump control unit J538(2) from cover (1).
39. Unclip cover (1) at retaining tabs (arrows) using removal wedge3409.
40. Disconnect fuel lines (2) and (3) from fuel delivery unit. Separate plug-in connectors .
41. ⚠ The fuel line is under pressure.Risk of injury to eyes and skin from fuel.Wear eye protection and protective clothing to avoid eye injuries and skin contact. Before loosening hose connections, wrap a cloth around the connection. Then release pressure by carefully opening the connection point. — Connect pressure testerVAS 6550 to fuel delivery unit (1).
42. Connect hoseVAS 6550/1 to fuel supply line (2) leading to engine.
43. Connect hoseVAS 6550/2 to connection (A) of pressure testerVAS 6550.
44. Connect fuel delivery unit (1) to pressure testerVAS 6550 using hoseVAS 6550/2.
45. Ensure plug-in connectors are secured properly by pulling.
46. Ensure that drain tap (C) on pressure testerVAS 6550(1) is closed.
47. Shut-off taps (A) and (B) on pressure testerVAS 6550(1) must be open.
48. Repeat Final control diagnosis to build up fuel pressure.
49. After pressure has built up, close shut-off tap (B) of pressure tester immediately. Lever is then at right angle to direction of flow.
50. Observe pressure drop on pressure gauge.
51. Check fuel line for leaks and damage.
52. Remove fuel delivery unit .
53. Check that all hose connections (arrows) are connected.
54. Check fuel lines for leaks and damage.
55. Pressure retention valve in fuel pump is defective.
56. Renew fuel delivery unit .

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