Evaporative Emissions System: Testing and Inspection: Diagnosis and Testing
Leak Detection Test, Performing
Diagnostic leak test occurs in guided fault finding.
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.
- Switch 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.
CAUTION!
Risk of destroying electrical components when battery is disconnected.
• Observe measures when disconnecting battery.
- With the ignition switched off, disconnect the battery ground (GND) - arrow -.
- Remove the rear shelf.
- Remove side trim panel.
- Remove the positive wire - 4 -.
- Disconnect the electrical connectors - 3 - on the connector station and remove the connector station from the control module bracket and lay it to the side.
- Remove the right rear relay and fuse carrier from the control module bracket and lay it aside - arrows -.
• Ignore - 1, 2 and 5 -.
- Disconnect the control module electrical connectors and remove the control module bracket - arrow - from the vehicle.
- Free up electrical wiring harness.
- Fold the insulation mat over the connection seal cover.
- Remove the left and right bolts on the locking flange cover - 1 to 4 - and then remove the cover.
- Check if the sealing ring under the left locking flange is OK or if the locking flange sealing ring on the fuel tank chamber is tightened correctly. Check also the fuel line connections - 1, 2, 3 -.
• Depending on the version, there may be 2 instead of 3 lines.
• Disregard - arrow -.
- Check if the sealing ring under the right locking flange is OK or if the locking flange sealing ring on the fuel tank chamber is tightened correctly. Check also the fuel line connections - 1, 2, 3 -.
• Depending on the version, there may be 2 instead of 3 lines.
• Disregard - arrow -.
• Observe installation notes for locking flanges => [ Installing ] Fuel Level Sensor 4 and => [ Installing ] Fuel Delivery Unit.
- Visually check all lines and hose connections on the fuel system and replace leaking lines, for example:
• Line from EVAP canister to EVAP canister purge regulator valve 1 (N80)
• Lines from EVAP canister to leak detection pump (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 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.
- Visually check the fuel system components and the fuel 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 hose clamps up to 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.