Checking holding pressure, vehicles with engine codes CWVA, CWVB, CHYA, CHYB — VW

🧭 Before you start

Release the supply line under pressure with a cloth around the joint, fit the tester hoses between the fuel lines and set the taps open with the drain tap closed. Build pressure with final control diagnosis, switch off and watch the gauge for 10 minutes. If the drop is too great, repeat with one tap closed to isolate the engine side, then retest at the fuel filter and at the delivery unit beneath the rear bench. A delivery unit that loses pressure has a defective retention valve and is renewed.

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

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

Don't miss

• The line is under pressure: wear eye protection and wrap a cloth around joints before opening them.
• Pull on every plug-in connector after fitting to make sure it has locked.
• Drain tap C must be closed and taps A and B open before pressure is built.
• Close the relevant shut-off tap immediately once pressure has built, or the isolation test means nothing.
• Pressure must not fall more than 1.0 bar within 10 minutes.
• Pressure loss traced to the delivery unit means a faulty retention valve; renew the unit.

Written for this job from the workshop steps below · TorqFix editorial.

🔧 Engine codes this applies to

📋 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. Check surfaces of fuel lines for leaks.
19. Check surfaces of fuel rail and injectors for leaks 24Injectors; Assembly overview - fuel rail with injectors.
20. Check injectors for leaks 24Injectors; Checking injectors.
21. Pull fuel supply line (arrow) off fuel filter. Separate plug-in connectors .
22. ⚠ 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.
23. Connect pressure testerVAS 6550 between fuel filter and fuel supply line using hoseVAS 6550/1 and VAS 6550/2.
24. Connect hoseVAS 6550/1 to fuel line leading to fuel tank.
25. Connect hoseVAS 6550/2 to connection (A) of pressure testerVAS 6550.
26. Use hoseVAS 6550/2 to connect fuel filter to pressure testerVAS 6550.
27. Ensure plug-in connectors are secured properly by pulling.
28. Ensure that drain tap (C) on pressure testerVAS 6550(1) is closed.
29. Shut-off taps (A) and (B) on pressure testerVAS 6550(1) must be open.
30. Repeat Final control diagnosis to build up fuel pressure.
31. After pressure has built up, close shut-off tap (A) of pressure tester immediately. Lever is then at right angle to direction of flow.
32. Observe pressure drop on pressure gauge.
33. Check fuel line for leaks and damage.
34. Check fuel filter for leaks and damage.
35. Proceed as follows to check residual pressure on fuel delivery unit:
36. Fold up bench seat General body repairs, interior72Rear seats; Removing and installing bench seat/individual seats.
37. Unclip cover (1) at retaining tabs (arrows) using removal wedge3409.
38. Disconnect fuel lines (2) and (3) from fuel delivery unit. Separate plug-in connectors .
39. ⚠ 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).
40. Connect hoseVAS 6550/1 to fuel supply line (2) leading to engine.
41. Connect hoseVAS 6550/2 to connection (A) of pressure testerVAS 6550.
42. Connect fuel delivery unit (1) to pressure testerVAS 6550 using hoseVAS 6550/2.
43. Ensure plug-in connectors are secured properly by pulling.
44. Ensure that drain tap (C) on pressure testerVAS 6550(1) is closed.
45. Shut-off taps (A) and (B) on pressure testerVAS 6550(1) must be open.
46. Repeat Final control diagnosis to build up fuel pressure.
47. After pressure has built up, close shut-off tap (B) of pressure tester immediately. Lever is then at right angle to direction of flow.
48. Observe pressure drop on pressure gauge.
49. Check fuel line for leaks and damage.
50. Remove fuel delivery unit .
51. Check that all hose connections (arrows) are connected.
52. Check fuel lines for leaks and damage.
53. Pressure retention valve in fuel pump is defective.
54. Renew fuel delivery unit .

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