Checking gas system for leaks — VW

🧭 Before you start

Fits: platform code 121

🔧 Engine codes this applies to

📐 10 workshop diagrams for BEH

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

📋 Procedure

1. Determine pressure in natural gas system. Determining pressure in gas system [Note: The gas shut-off valves are closed electrically upon pulling out the relay for gas shut-off valves J908. The gas system can still be filled.This will deactivate the gas system and it prevents the leakage of larger amounts of gas through any possible leaks after the gas system has been filled.]
2. Drive to the petrol station in petrol mode.
3. Drive back to the workshop in petrol mode.
4. Before driving the vehicle into the workshop, reactivate natural gas mode by inserting the relay for gas shut-off valves J908 into the relay carrier. [Note: The fuel tank shut-off valves will be activated for only two seconds after the ignition has been switched on.A mechanical »clicking« noise can be heard.During actuation of the fuel tank shut-off valves, listen carefully for the sound of leaking gas in the section which was repaired.If the injectors are not activated, perform an adaption drive to activate the gas system.To ensure successful results from the adaption drive, the engine must repeatedly be operated with partial load during the drive.To check whether the natural gas system has been successfully actuated, consult the fuel gauge of the natural gas system]
5. Set up a safety area, and observe safety precautions Safety precautions when working on natural gas system.

6. Set the petrol mode using the function Release pressure in natural gas high-pressure line.
7. Wait until no sound of escaping gas can be heard.
8. Drive the vehicle into the workshop.
9. Loosen all threaded connections already loosened during repair work, and tighten them according to specifications.
10. Drive vehicle out of workshop.
11. Deactivate petrol mode using function Release pressure in natural gas high-pressure line.
12. Check if the sound of escaping gas can be heard.
13. Drive the vehicle into the workshop.
14. Perform required leakage test after working on the high-pressure section , or the required leakage test after working on the low-pressure section Checking gas system for leaks after working on the low-pressure section.

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