Evaporative Emissions System: Testing and Inspection: Diagnosis and Testing

Leak Detection Test, Performing

Special tools, testers and auxiliary items required

• Hose Clamps Up to 25 mm Dia. (3094)

Diagnostic leak test occurs in "Guided Fault Finding" using the vehicle diagnostic tester.

Checking Fuel Supply and Tank Ventilation Systems for Leaks

• 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.

- Turn off ignition.

- Check whether the fuel filler cap of the fuel tank was completely sealed for the test.

- Check whether seal of fuel filler cap was damaged or crimped. Replace if necessary.

- Remove rear seat bench.

- Unclip catches - arrows - of right connector flange cover.






• Observe installation notes for locking flanges => [ Installing ] Fuel Delivery Unit and => [ Installing ] Fuel Delivery Unit.

AWD Vehicles:

- Unclip the retainers - arrows - of the cover for left sealing flange.






• Follow the installation instructions for the locking flange => [ Installing ] Fuel Level Sensor 2 (G169).

All Vehicles:

- Check sealing rings seals under locking flanges are OK and lock rings are properly tightened on fuel tank. Also check the fuel line connections.

- Visually check all wires and hose connections of fuel supply system and replace leaking lines, for example:

• Line from EVAP canister to Evaporative Emission (EVAP) Canister Purge Regulator Valve 1 (N80)

• Lines from EVAP canister to Leak Detection Pump (LDP) (V144).

• Line from fuel tank to EVAP canister (below heat shield for EVAP canister).

• Lines for tank ventilation (beneath right rear wheel housing liner).

• Fuel lines to engine.

• Leaks at lines and components of the tank system can sometimes be located using a nonflammable, 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 the fuel system components and tank ventilation system:

• Fuel tank

• EVAP canister

• Leak detection pump

• EVAP canister purge regulator valve 1

• 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 (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.