Pressure/Vacuum Relief Fuel Cap

WARNING: This page is about a different car, the 1995 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.

This system consists of a sealed filler cap with integral pressure/vacuum relief valve. Fuel system vacuum relief is provided after 1.0 in. Hg of vacuum; pressure relief is provided after 1.8 psi (.13 kg/cm² ). Under normal conditions, fill cap allows air to enter fuel tank as fuel is used, while preventing vapors from escaping.