Evaporative Emission (EVAP) Canister System, Checking For Proper Seal
Evaporative Emission (EVAP) Canister System, Checking For Proper Seal
NOTE:
- Secure all hose connections using hose clamps appropriate for the model type.
- Always replace seals and gaskets.
Test sequence
- Connect diagnostic tester.
- Start engine and let run at idle for at least 15 minutes.
- In diagnostic function "33 - OBD", select "Mode 8: Tank leak test".
- Select the "Test-ID 01: Tank leak test" and check specified value at idle.
- Specified value: Test OK
NOTE:
- If the accelerator pedal is depressed during the test, the test will be aborted.
- To repeat the tank leak-tightness test switch the ignition off, start the engine again, and let it run at idle.
If specified value is obtained:
- End diagnosis and switch ignition off.
If specified value is not obtained:
Check tank system and tank ventilation for proper seal
- Check whether the fuel tank fuel filler cap was completely sealed for the test.
- Check whether the seal of the fuel filler cap is damaged or pinched and must be replaced.
- Remove connection hose from Leak detection pump (LDP) -V144- at Evaporative Emission (EVAP) canister and close it.
- Repeat function test.
If malfunction persists:
- Remove cover from Evaporative Emission (EVAP) canister at bottom of spare wheel well.
- Remove sealing pieces above vent lines.
- Check connecting lines and hoses between Leak detection pump (LDP) -V144- and Evaporative Emission (EVAP) canister for proper seal. See EVAP canister/tank leak diagnostic system - Component overview.
- Repeat function test.
If malfunction persists:
- Remove luggage compartment floor.
- Push forward the left 1/3 backrest of rear seat, if necessary.
- Remove cover for connector flange -arrows-.
- Remove rear seat bench.
- Remove locking flange cover bolts -arrows-, left and right. Check whether seals under connector flanges are OK and union nuts are properly tightened.
- Check fuel line connections.
- Visually check all lines 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 (in engine compartment)
- Lines from Evaporative Emission (EVAP) canister to Leak Detection Pump (LDP)
- Line from fuel tank to Evaporative Emission (EVAP) canister (below cover for EVAP canister)
- Lines from EVAP system (under rear right wheel housing liner)
- Fuel lines to engine
NOTE:
- Leaks at lines and components of fuel supply system can sometimes be located using a non-flammable, environmentally sound engine leak detection spray (e.g. G 001 800 A1).
- Pressure of (max. 70 mbar) can be applied to the fuel system via the test connection (in engine compartment). Leaks can be determined using engine leak detection spray. When doing this, bubbles form at leaking areas.
- Repeat function test.
If malfunction persists:
- 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:
- Also check vacuum hose setup from engine compartment to leak detection pump for proper seal
- Because of shape or function of these components it is not always possible to find leaks by applying spray. It may be necessary to clamp off the relevant component using 3094 hose clamps and initiate leak detection diagnostic. If leak is no longer detected, the component that was clamped off is faulty. If clamp is placed directly on the diagnostic pump and a leak is still detected, then the diagnostic pump itself is leaking.
- Observe installation notes for connector flanges.
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory see "Mode 3: Check DTC memory". Mode 3: Check DTC Memory
2. If necessary, erase DTC memory see "Mode 4: Reset/erase diagnostic data". Mode 4: Reset/Erase Diagnostic Data
3. Generate readiness code. Readiness Code, Generating
- End diagnosis and switch ignition off.