Gearbox removal & installation: Emptying natural gas fuel tank — VW

🧭 Before you start

Fits: platform code 121

• Renewed: it if necessary

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• Ensure that fuel tank shut-off valve is flush with rigid support.
• Ensure that the ratchets of the tensioning straps are offset, as shown in illustration.
• When lashing down, ensure that surface of fuel tank is not damaged.
• When doing so, ensure that seal (3) is seated correctly.
• Screw on adapter hand-tight. Do not use any tools for this, e.g. pliers or similar.

🔧 Engine codes this applies to

📐 41 workshop diagrams for CDGA

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. Observe safety precautions when working on natural gas system .
4. ⚠ The evacuation process must be carried out outdoors.Ensure that there are no sources of ignition and no open fires near the vehicle and the fuel tank.There is a danger of explosion!The fuel tank must always be securely lashed to the engine and gearbox jack.This will prevent the fuel tank from falling.If the fuel tank is not securely lashed down, any work on the fuel tank is prohibited. — Remove respective fuel tank .
5. Align adjustable supports of gearbox support T40173 relative to fuel tank, and secure them.

6. In order to properly secure adjustable supports, pull lever (1) downwards and position it such that the fuel tank can be properly secured.
7. Fit fuel tank (1) to gearbox support T40173 with tensioning strap T10523 as shown in illustration.
8. Secure fuel tank using tensioning strap T10523 to prevent it falling down.
9. Ensure that fuel tank shut-off valve is flush with rigid support.
10. Turn fuel tank so that connection for fuel line on fuel tank shut-off valve points vertically downwards.
11. Ensure that the ratchets of the tensioning straps are offset, as shown in illustration.
12. Securely lash fuel tank (1) to gearbox support T40173 using the two tensioning straps T10523.
13. When lashing down, ensure that surface of fuel tank is not damaged.
14. If necessary, protect surface with suitable workshop equipment.
15. Secure bracketVAS 523 001/6 on gearbox support T40173 as shown in illustration.
16. Use one or two bolts for this (arrows).
17. Insert gas discharge pipeVAS 523 001/1 into guide (arrow) on bracketVAS 523 001/6.
18. Screw suitable adapterVAS 523 001 onto gas discharge pipe (4).
19. When doing so, ensure that seal (3) is seated correctly.
20. Screw adapter (2) onto fuel tank shut-off valve(1).
21. Screw on adapter hand-tight. Do not use any tools for this, e.g. pliers or similar.
22. If necessary, seal open connection with sealing cap (1) from adapterV.A.G 1274B/12 A-1.
23. Unscrew plug (arrow) on fuel tank shut-off valve(1).
24. Unscrew nut (arrow) on fuel tank shut-off valve(1) and remove it.
25. Pull solenoid (2) in (direction of arrow) off fuel tank shut-off valve(1).
26. Fit magnetic release tool T10349 on valve. [Note: The magnetic release tool T10349 must remain fitted onto the valve during the entire emptying process.It prevents the valve from becoming jammed.]
27. Fit handwheel T50026 to manual shut-off mechanism (arrow) on fuel tank shut-off valve.
28. ⚠ Establish a safety zone around the fuel tank, which must not be entered while the fuel tank is emptied. Leave the safety zone after you have opened the manual shut-off valve.Inhaling natural gas can lead to poisoning of the respiratory tract.When no more natural gas escapes from the fuel tank, perform a back pressure test . — Carefully open fuel tank shut-off valve in (direction of arrow) using handwheel T50026 until natural gas escapes.
29. After 1 or 2 seconds, close fuel tank shut-off valve.
30. Check connections between gas discharge pipe (4) and fuel tank shut-off valve(1) for leaks.
31. To do so, use gas leak detectorVAS 6227 and commercially available leak detection spray.
32. Check seal (3) for damage, and renew it if necessary.
33. Check connection between gas discharge pipe (4) and fuel tank shut-off valve(1) for soiling, and tighten it if necessary.
34. If the leak cannot be rectified, the gas discharge pipe must not be used.
35. Carefully open fuel tank shut-off valve in (direction of arrow) using handwheel T50026 until natural gas escapes.
36. Carefully open fuel tank shut-off valve as far as possible without triggering the »restrictor valve«.
37. The fuel tank shut-off valve must not be opened completely. [Note: Depending on the tank pressure, the fuel tank shut-off valve can immediately be opened completely.Fully opening will trigger the "“restrictor valve”". Then only a small amount of gas can escape.]
38. To reset the restrictor valve, the pressure must be equalised by closing the »manual shut-off«.
39. Close valve, then open it again making sure not to open it too far this time.
40. After approx. 2 minutes, the valve can be opened completely.
41. When natural gas no longer escapes from fuel tank, the manual shut-off valve must be closed again.
42. Perform back pressure test to ensure that the gas tank has been sufficiently emptied .

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