Evaporative Emissions System: Testing

Drain gasoline from fuel tank, place fuel cap tightly on filler neck and close fuel flap door completely. Remove evaporation tube from air cleaner housing and remove fuel delivery hose from fuel tank. Connect a water column manometer that reads to 17.55 (400 mm) or more to pipe as shown in illustration. Blow clean compressed air into air cleaner connection of evaporation tube until manometer indicates 14.17" (360 mm) of water.

System is functioning correctly if it takes 5 minutes or longer for pressure to drop to 1.97" (50 mm) of water.

Fig 1: System Test

Courtesy of SUBARU OF AMERICA, INC.