Fuel Filler Cap: Testing and Inspection

Checking Filler Cap Pressure Relief Valve







Set pressure regulator on special tool 16 1 171 fully in direction.
Connect special tool 16 1 171 via compressed air line (1) to garage compressed air system (8... 10 bar).
Connect pressure sensor (2) of Diagnosis and Information System with a measuring range of 0.. .3.5 bar.







Select special tool 16 1 172 or 16 1 173 matching vehicle's filler cap and attach to quick release coupling of special tool 16 1 171.
Install filler cap on selected special tool (3).







NOTE: Only the absolute pressure is indicated in the display of the Diagnosis and Information System (DIS). The current ambient air pressure is already displayed without additional pressurization.


Check testing equipment for leaks.
Select "Measurement" function on Diagnosis and Information System (DIS).
Set measuring range according to pressure sensor to 0-3.5 bar.
Increase pressure by 0.2 bar with pressure regulator on special tool 16 1 171.
Using special tool 13 3 010, disconnect delivery line from special tool 16 1 171 to tank filler neck.
Wait 60 secs.

Read off final pressure value and compare with starting pressure value.

Measurement evaluation:
Pressure drop > 0.012 bar Testing equipment leaking.
Check connection points for leaks.

Check filler cap pressure relief.
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.

Measurement evaluation:
Pressure drop > 0.012 bar Filler cap pressure relief valve faulty.
Replace filler cap.