Nearly all the replacement caps today don't work properly.
The valve in the vent often sticks shut and doesn't allow fresh air into the tank to replace the volume of fuel removed by the fuel pump. This can damage the tank and the pump.
If your cap looks like this one, take a screwdriver and fold back those metal ears holding the plastic parts in place.
Take everything out and remove the plastic parts.
Behind the tan plastic part with the holes in it is a rubber valve and spring. Remove that valve and then put everything else back together.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
