Evaporative Line Check

Disconnect vapor line from ventilation valve system and connect "U" tube pressure gauge to disconnected vapor line. Gradually apply low air pressure into "U" tube so that difference of water level should be 14" (356 mm). See Fig 4.
Bind the inlet of the "U" tube and leave bound for 5 minutes. If water drops no more than 1" (25 mm) after 5 minutes, evaporative line is in good condition.

Fig 1: Check & Cut Valve
Courtesy of MAZDA MOTORS CORP.

Fig 2: RX-7 Ventilation & Check Valve
Courtesy of MAZDA MOTORS CORP.

Fig 3: Fuel Evaporation System (Typical)
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Fig 4: Testing Evaporative Lines Using "U" Tube Pressure Gauge
Courtesy of MAZDA MOTORS CORP.