Fuel overflowing gas cap.

[CM II]

I filled the tank on my 64 a 1/2 mile from home and a few hours later gas was leaking from the cap. I took the cap off and about 3 cups of gas came spilling out. The cap looks original and is stamped vented. I put a new Summit fuel pump on 6 months ago. The outside air temperature did not go up and it was about 74°F outside. I pumped the bumper up and down a few times on each side and the fuel continued to pour out.

This is the first time this has happened and I am puzzled as to what would cause this situation. I don't know if the tank is vented.

Chuck

[paulr]

I don't know if the tank is vented.

Chuck

If it’s an OEM 64MY tank it is not vented. Spectra sells reproduction tanks for 64s that are vented now but you’d have to know if you have a replacement because the vent is on top of the tank out of view.

Vent plus the cap you have would prevent the problem I believe. Sorry, that doesn’t help much.

[Inspector]

If the gasoline in the underground storage tank was cold enough, there may have been enough expansion during the time the gas sat in your gas tank.

[64ZCODE]

Plus the filler neck on the '64 rises up to the cap at such a gradual angle that a minor rise in gas level in the tank would result in a larger flow out the cap than one might expect.