Leak Detection Test, Performing
Leak Detection Test, Performing
Special tools, testers and auxiliary items required
• Vehicle diagnostic, testing, and information system (VAS 5051B) with Diagnostic Cable (VAS 5051/5A)
• Hose clamps up to dia. 25 mm (3094)
• Secure all hose connections with hose clamps appropriate for the model.
• Replace seals and gaskets when performing repair work.
Procedure
• Parking brake engaged.
• Selector lever in position P or N.
• Engine running at idle speed or with brakes actuated and accelerator fully depressed (elevated engine RPM).
• Electrical consumers switched off (Radiator fan must not run during test).
• Air conditioning system switched off.
• (VAS 5051B) connected with (VAS 5051/5A), Vehicle Self-Diagnosis selected.
• No faults in DTC memory.
• Intake air temperature less than 90 °C => Display group 004, display field 4.
• Coolant temperature less than 95 °C => Display group 004, display field 3.
Observe safety precautions. Refer to => [ Safety Precautions ] Fuel Supply System.
Observe rules for cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply System.
Display on (VAS 5051B):
- Tap "On Board Diagnostic" in selection - 1 - and activate by tapping the -> button.
Display on (VAS 5051B):
- Tap "01 - Engine Electronics" vehicle system in selection - 1 - and activate by tapping the -> button.
Display on (VAS 5051B):
- Tap "006 - Basic Setting" function in selection - 1 - and activate by pressing the -> button.
Display on (VAS 5051B):
- In button field - 1 -, press buttons 7 1 for "display group 071" and confirm entry by pressing Q button.
Display on (VAS 5051B):
- Check reading in display field - 1 -.
• Specified value: "Reed closed".
• If "Reed closed" is displayed, continue test.
• If the reading on the display shows "Reed open": Briefly open the cap of the fuel tank to relieve pressure - thereby the reed contact will close again.
- Press the Activate button - A - to start the basic setting.
Display on (VAS 5051B):
- Check reading in display field - 4 -.
• Specified value: "Test ON".
The system test takes several minutes.
- Check reading in display field - 4 -.
• Specified value: "Syst.O.K.".
The system is sealed, the test is ended.
- End function "006 - Basic setting" by pressing <- button.
Fault indication
If a malfunction was recognized during the system test, the malfunction is indicated afterward.
On (VAS 5051B) display in display field - 4- -:
• In case of malfunction: Syst. not O.K.
- Check readings of the diagnosis in display field - 2 -.
• "Small leak" or "Large leak".
- End function "006 - Basic setting" by pressing <- button.
If the system has recognized a small or large leak:
- Check fuel supply and tank ventilation systems for leaks.
- Afterwards, perform the leak diagnosis again.
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.
- Fold rear seat right backrest forward, if necessary.
Wagon:
- Remove luggage compartment cargo floor - 1 -.
• Ignore - item 2 -.
- On vehicles without air suspension, unclip right sealing flange cover retainers - arrow -.
- On vehicles with air suspension, unscrew spreader pins - arrows - and remove cover - 1 -.
All:
- On vehicles with air suspension, remove bolts - arrows -.
- Remove pressure tank - 2 - and set aside with line connected - 1 -.
• Do not stretch or kink line.
Sedan:
- Release the retaining tabs - arrows -.
- Fold open the retaining tabs - 1 - and - 3 - toward the rear.
- Fold the cover - 2 - toward the front - arrow -.
All:
- Unbolt cover - arrows -.
- Remove rear seat bench.
- Unbolt cover for locking flange, left and right - arrows -.
• Observe installation notes for locking flanges. Refer to => [ Fuel Delivery Unit ] Fuel Delivery Unit and => [ Fuel Level Sensor 2 ] Fuel Level Sensor 2.
All:
- Check whether seals under locking flanges are OK and union nuts 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, e.g.:
• Line from EVAP canister to Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80)
• Lines from EVAP canister to Leak Detection Pump (LDP) (V144).
• Line from fuel tank to EVAP canister (below cover 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.
- Perform a visual inspection on the fuel system components and tank ventilation system:
• Fuel Tank
• EVAP canister
• Leak detection pump (LDP)
• Evaporative emission (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 defective. If clamped off directly at the leak detection pump and a leak is still indicated, the leak detection pump itself is leaking.