Fuel Vapor Rollover Valve
WARNING: This page is about a different car, the 1995 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
Remove fuel vapor valve. Hold valve in level upright position. Blow air into port (hose barb). Air should flow through valve to lower port. Turn valve upside down. Air should not flow. Replace valve as necessary.