Crown Victoria V8-281 4.6L SFI (1998)
Fuel Filler Cap: Description and Operation
The fuel tank filler cap is a sealed cap with a built-in pressure-vacuum relief valve::
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fuel system vacuum relief is provided after negative 2 kPa (0.28 psi).
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provides pressure relief above 14 kPa (2 psi).
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under normal operating conditions, operates as a check valve, allowing air to enter the fuel tank as fuel is used while preventing fuel vapors from
escaping the fuel tank through the fuel tank filler cap.
