Have an '89 Imark RS DOHC put back into commission 2 years ago. Fuel tank, pump and hoses at the tank replaced at that time.

Broke the vacuum nipple on the vapor canister a month ago and observed no ill effects. Looking for a new one. Figured a '90 Geo Storm GSI canister
will work.

Here's the problem. Left it parked a few days while out of town. It was upper 90's while we were gone. Got back and noticed a puddle of gas under the tank. Upon inspection I realized the the leak came from the top of the tank. When I removed the gas cap the pressure release was greater than normal. The leak hasn't happened since then. Have been leaving the cap a little loose.

I'm wondering if excess pressure built up in the tank due to the inoperative canister, excesive heat and no release of tank pressure since the car was left parked. The tank was 1/4 full containing more vapor than liquid. I was thinking the vapor expands easier than liquid and an increase in pressure for the fuel pushed it up and out of the tank via a fuel line.

Any help is appreciated.