Fuel Filler Cap: Testing and Inspection

16 11 130 - Checking tank cap pressure relief valve





Special tools required:
- 13 3 010 13 3 010 Hose Clip
- 16 1 171 16 1 170 Tester with Test Adapter
- 16 1 172 16 1 170 Tester with Test Adapter
- 16 1 173 16 1 170 Tester with Test Adapter





Necessary preliminary tasks:
- Remove tank cap





Turn pressure regulator on special tool 16 1 171 16 1 170 Tester with Test Adapter counterclockwise up to stop.
Connect special tool 16 1 171 16 1 170 Tester with Test Adapter via compressed air line (1) to workshop/garage compressed air system (8...10 bar).
Connect pressure sensor (2) of Diagnosis and Information System with a measuring range of 0...25 bar.





Select special tool 16 1 172 16 1 170 Tester with Test Adapter or 16 1 173 16 1 170 Tester with Test Adapter matching vehicle's filler cap and attach to quick release coupling of special tool 16 1 171 16 1 170 Tester with Test Adapter.
Install tank cap on selected special tool.





Check testing equipment for leaks!
Select "Measurement" function on Diagnosis and Information System (DIS).
Increase pressure by 0.2 bar with pressure regulator on special tool 16 1 171 16 1 170 Tester with Test Adapter.
Using special tool 13 3 010 13 3 010 Hose Clip, disconnect supply line (1) from special tool 16 1 171 16 1 170 Tester with Test Adapter to fuel filler neck.
Allow a rest period of approx. 20 secs.
Read off and note down starting pressure.
Wait approx. 120 secs.
Read off final pressure value and compare with starting pressure value.





Measurement evaluation:
- Pressure drop up to 0.01 bar:
System OK
- Pressure drop over 0.02 bar:
System leaking beyond permitted levels
If system is leaking, check connection points for leaks.

Check tank cap pressure relief valve.
Follow same test procedure as for "Checking testing equipment for leaks".
Increase pressure by 0.3 bar with pressure regulator on special tool 16 1 171 16 1 170 Tester with Test Adapter.
Measurement evaluation:
- Pressure drop up to 0.01 bar:
Tank cap pressure relief valve OK
- Pressure drop over 0.02 bar:
Tank cap is leaking and must be replaced