Fuel Tank: Testing and Inspection

Tank Leak Diagnostic, Performing

Special tools and test equipment







- VAS 5051 with VAS 5051/1

NOTE:
- Fasten all hose connection with hose clamps used in production.
- Always replace seals, O-rings and gaskets.

Checking fuel supply and tank ventilation system for leaks

NOTE: The following describes areas in the fuel supply and ventilation system that should be checked for possible leaks. After making necessary repairs, perform leak test again to ensure that all leaks were successfully repaired.

- Switch ignition off.
- Check if fuel filler cap was completely closed for test.
- Check if seal of fuel filler cap is damaged, replace if necessary.

Limosine:
- Remove cover for sender for fuel gauge located under liner in luggage compartment.

Avant:
- Remove cover for sender for fuel gauge located under liner in luggage compartment.

All:







- Rear closing flange: Remove liner for luggage. Unbolt closing flange.

Vehicles with all wheel drive:
- Remove rear seat







- Remove the screws -arrows- for the catch flange cover.

NOTE: Observe installation notes for closing flanges.

All:
- Check whether seals under connection flanges are OK and ring nuts are properly tightened. Also check if fuel line connections are tight.
- Visually check all lines and hose connections of tank ventilation system and replace leaky lines, e.g.:
- Line EVAP canister to Evaporative Emission (EVAP) Canister Purge Regulator Valve (in engine compartment).
- Lines from EVAP canister to Leak Detection Pump (LDP) (under left rear wheelhousing liner).
- Line from fuel tank to EVAP canister (beneath cover for EVAP canister)
- Lines from EVAP system (tank ventilation system) below right rear wheelhousing liner.
- Fuel lines to engine.

NOTE: Leaks at lines and components of fuel supply system can sometime be located using a non-flammable, environmentally sound leak detection spray. For this, initiate leak test several times in sequence to build pressure in the system. Leaks can be detected via bubbles forming at the leak.

- Visually check components of fuel supply system and EVAP system.
- Fuel tank
- EVAP canister
- Leak Detection Pump (LDP) -V144-
- Evaporative Emission (EVAP) canister purge regulator valve -N80-

NOTE: Because of the shape or function of these components it is not always possible to detect leaks by applying spray. It may be necessary to clamp off the relevant component using 3094 hose clamp and initiate the leak detection diagnostic. If the leak is no longer detected, the component that was clamped off is faulty. If the clamp is directly on the diagnostic pump and a leak is still detected, then the diagnostic pump itself is leaking.

- Checking Evaporative Emission (EVAP) Canister Purge Regulator Valve -N80-.