Gas Cap Vent

[shonutt]

Well I Had To Replace My Gass Cap I Got A Stant Brand From My Work ..it Has A Venting Feature Meaning I Can Vent It Or I Can Make It Sealed ..whitch Do I Want Sealed Or Vented ? What Is The Differance ..any Harm In Doing One Or The Other ? Please Help

 

[Rockledge]

The '92 Ford Manual says of the Taurus EVAP system:

Sealed Fill Cap

The fill cap is a sealed cap with a built-in pressure-vacuum relief valve. Fuel system vacuum relief is provided after negative 3.45 kPa (0.50 psi) and pressure relief above 11 kPa (1.6 psi). Under normal operating conditions, the fill cap operates as a check valve, allowing air to enter the tank as gasoline is used, while preventing vapors from escaping the tank through the cap.