The new gas caps, like just about everything else you buy today, are absolute crap. The valve inside, meant to vent the tank doesn't work. You end up having vacuum pressure build up as the fuel pump sucks out the gas because no air can enter to fill the void.
Take the cap apart and remove the little valve and spring.
Bend those two ears at 12:00 and 6:00 and remove the valve assembly. Behind the tan plastic part with 5 holes is a rubber valve and spring. Pull it out and put the rest back together.
It will work as it should after that.
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)
