3-Way Check Valve

Note direction of valve installation. Remove check valve. Cap check valve port "C". See Fig 1 . With 1.5 in. Hg of vacuum applied to port "A" of check valve, air should flow. With 2.8 in. Hg of vacuum applied to port "B" of check valve air should flow. Replace check valve as necessary.

Fig 1: Identifying Two-Way Check Valve

Courtesy of MAZDA MOTORS CORP.