I lost my old cap after setting it on the running board and driving off. Back tracking my path home yielded nothing. The cap is supposedly vented but when I remove it on a hot day, I get a substantial blast of gas fumes. Parts guy says the cap is only vented one way so as not to let fumes out but replacement air in only. He suggested I drill a small hole in the cap but I wonder about drilling a hole in what must be the check valve on the inside of the cap. What do you guys think?
I'm also going to epoxy some neodymium magnets to the cap so I can just stick it on the cab when I fill up so at least I won't lose it if I forget to put it back on.
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)
If your cap has blue plastic on the underside, simply drill a 1/8" hole in the blue plastic just off the center of the round blue piece. Air will now be able to vent in and out as originally intended. I have done this on four different trucks. Works like a champ.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
I bought the replacement from a local auto parts place but when I found out about the pressurized tank I called NAPA and they said they had the correct one. Turned out to be identical to the other replacement but in a NAPA box. In the morning I'm going to be working on it. Thanks for the replies!
I have a strict and simple procedure - when fueling my ‘54 I place the gas cap IN THE TRUCK BED , no exceptions. (I once lost a really nice Leatherman by placing it on the bumper while changing hit balls. Hard lesson.)
Yeah Wave, same here. I did the same thing with my Packard gas cap that had managed to survive almost 90 years without a scratch. I set it on the bumper and then heard it rattle off as I turned right onto the street. I immediately pulled over and ran back to get it just in time to see a car come by and run it over and completely destroy it.
Truck caps go in the bed, car caps go in my pocket.
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)
Never owned a car in my life. Caps go in pocket. Curious though my pickup with a relocated fuel tank and filler to fender, vents upon itself but no vent at the cap. Works fine.
~ BD. "You won't find me in an old folks home" Pioneer Florida Cracker 1958 Apache Stepside 1958 Apache 1/2 ton Panel 1959 Apache 1/2 ton Panel
Same gas cap and vent arrangement I used on my '57 GMC, Guitplayer. My tank was a junkyard special I pulled from a mid-80s Mazda pickup.
Last edited by Bill Hanlon; 07/10/20264:12 AM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
