Checking fuel supply and tank ventilation systems for leaks

NOTE:

The following describes individual areas in the fuel supply and ventilation systems where leaks are possible. After repairing a possible leak, perform a leak test to ensure that leak was successfully repaired.

Switch off ignition.
Check whether fuel filler cap of fuel tank was completely sealed for test.
Check whether seal of fuel filler cap was damaged or crimped. Replace if necessary.
Remove trim for luggage compartment floor.

NOTE:

Observe installation notes for locking flanges: Left Installing , right Installing .

Check whether seals under locking flanges are OK and lock rings are properly tightened on fuel tank. Also check fuel line connections.
Visually check all wires and hose connections of fuel supply system and replace leaking lines, e.g.:

Line from Evaporative Emission (EVAP) canister to Evaporative Emission (EVAP) Canister Purge Regulator Valve N80 and Evaporative Emission (EVAP) Canister Purge Regulator Valve 2 N333 (in engine compartment)
Lines from EVAP canister to Leak Detection Pump (LDP) V144 and to Evaporative Emission (EVAP) Canister Purge Solenoid Valve N115.
Line from fuel tank to EVAP canister (below cover for EVAP canister).
Fuel lines to engine.

NOTE:

Leaks at lines and components of tank system can sometimes be located using a non-flammable, environmentally compliant leak detection spray. For this, initiate leak diagnostic several times in sequence to build up pressure in the system. At leaking areas, bubbles will form.

Perform a visual inspection on fuel system components and tank ventilation system:

NOTE:

Due to the form or function of the components, leaking areas may not always be localized by spraying on leak detection spray. It may be necessary to clamp off the relevant component using hose clamps up to dia. 25 mm 3094 and initiate tank leak detection diagnostic. If the leak is no longer indicated, the component that was clamped off is faulty. If clamped off directly at the leak detection pump and a leak is still indicated, the leak detection pump itself is leaking.