Wagoneer L6-258 4.2L VIN C 2-bbl (1982)
Fuel Filler Cap: Description and Operation
The fuel filler cap uses a two-way (vacuum and pressure) relief valve that is closed during normal operating conditions. The relief valve is
calibrated to open only when pressure in excess of 0.8 psi or vacuum in excess of 0.1 inch Hg develops in the fuel tank. When vacuum or pressure
is relieved, the valve returns to its normally closed position.
Some filler caps have a rollover check valve. This valve consists of a stainless steel ball in a plastic housing mounted on the fuel tank side of the
cap. Should the vehicle be overturned or tipped sufficiently, the steel ball drops into an orifice closing the vent to prevent fuel leakage.
NOTE: It is normal to occasionally encounter an air pressure release when removing the fuel filler cap.
