Checking Fuel Tank and Tank Ventilation System For Leaks

Checking Fuel Tank And Tank Ventilation System For Leaks


NOTE:
The following procedure is only applicable to vehicles without the tank leak diagnosis module.
Check tank venting system if a leak is suspected.


The following conditions must be observed to obtain plausible measuring results:
- Content of fuel tank:
1. Max. 90% (approx. 83 I)
2. Min. 13% (approx. 12 I, reserve indicator lamp "off").
- Park the car in the workshop at least 2 hours before the test so that the fuel temperature is approximately that of the workshop temperature (ideal fuel temperature approx. 10...20 °C).
- Never refuel the vehicle directly prior to the leak test due to the strong emission of gas by the fresh fuel.







Removing fuel tank underbody protection on left.
Unlock connection (3) on carbon canister and detach.
Using special tool 16 1157 seal opening for connection (3) on carbon canister.







Remove tank cap and connect special tool 16 1 174 to tank filler neck.
Using adjusting wheel (1), clamp special tool 16 1 174 firmly to tank filler neck.


CAUTION: Set pressure regulator on special tool 16 1 171 fully in direction.







Connect special tool 16 1 171 using compressed air line (1) to garage compressed air system (8.. .10 bar).
Connect pressure sensor (2) of Diagnosis and Information System with measuring range of 0.. .3.5 bar.


CAUTION Do not connect fast-release coupling (3) of special tool 16 1 171 yet.


Select "Measurement" function on Diagnosis and Information System (DIS).
Set measuring range in accordance with pressure sensor to 0-3.5 bar.
Using pressure regulator on special tool 16 1 171, increase pressure by 0.050 bar.
Connect special tool 16 1 174 to fast-release coupling of special tool 16 1 171.
Using pressure regulator on special tool 16 1 171, reset gauge pressure in fuel tank to 0.050 bar.


CAUTION Do not under any circumstance increase pressure by more than 0.100 bar as this would result in damage to the fuel tank and venting system.


Using special tool 13 3 010, disconnect supply line from special tool 16 1 171 to tank filler neck.
Allow a rest period of approx. 20 secs.
Read off and note down starting pressure value.
Wait 60 secs.
Read off final pressure value and compare with starting pressure value.

Measurement evaluation:
Pressure drop between Measure again.
0.008 and 0.010 bar.
Pressure drop in 60 secs. System leaking beyond permitted levels.
greater than 0.010 bar Carry out leak test.