Test EVAP System
WARNING: This page is about a different car, the 1999 Audi A8, 1998 Audi A8, and 1997 Audi A8. However, it is still accessible from the selected car via links, so may be relevant.
If vehicle is not LDP-equipped:
- Plug or clamp EVAP canister outlet and proceed to step "Continued for all vehicles" (below).
If vehicle is LDP-equipped:
- Plug or clamp LDP inlet (filter side) using Special Tool No. 3094 or equivalent.
- Attach fuel cap adapter to filler neck (arrow) and test hose to adapter.
- Turn control valve from "Hold" to "Test".
- Allow fuel system to pressurize.
NOTE:
Fuel system pressurization depends on volume of fuel system and amount of fuel in tank.
If fuel system pressurization does not stabilize:
- Verify all fuel system outlets have been sealed before continuing.
CAUTION:
Clamp only soft rubber lines when isolating a leak. To avoid risk of damage, never clamp hard plastic lines!
NOTE:
Any flow shown on flow meter indicates a leak. Flow before flow meter flag set at vehicle leak standard may indicate a sporadic DTC.
If flow meter on tester registers flow near or above preset pressure:
- Clamp off hose (arrow) leading from EVAP purge regulator valve -N80- to intake manifold (pictured: AHA engine in A6).
If flow stops:
- Replace EVAP purge regulator valve -N80- and repeat test before continuing.
If meter indicates no flow after test:
- Perform a quality check and return vehicle to customer.
If flow continues, proceed as follows:
Method 1: Locate leak with smoke generator
- Connect leads from smoke generator to vehicle battery.
- Use smoke generator trigger to charge fuel system with smoke.
- Inspect complete EVAP system for escaping smoke.
Method 2: Locate leak with ultrasonic tester
General search: tester only
Localized search: tester with extension (on left in illustration)
If leak cannot be located:
- Disconnect and plug or clamp shut EVAP lines to isolate fuel tank, using Special Tool No. 3094 or equivalent, before continuing.
CAUTION:
Clamp only soft rubber lines when isolating a leak. To avoid risk of damage, never clamp hard plastic lines!
If flow stops:
- Reconnect EVAP lines to search area that was isolated
If leak or source of fuel odor cannot be found:
- Contact Audi Dealer Technician Helpline.
CAUTION:
Under no circumstances should the vehicle be returned to the customer without proper diagnosis and repair.
When leak has been located:
- Repair leak and repeat EVAP system test.
- Perform quality check and return vehicle to customer.
NOTE:
- Because leak may be at top of fuel tank, it may not be possible to locate through fuel pump/sending unit access plate.
- Fuel tank may need to be lowered to locate the leak.