Gas spewed out my gas tank in my 1991 civic hatchback while running. drove about 100 miles in 80 degree weather and parked idling for about 5 min when i looked over and gas was spewing out tank while gas cap was still on. Turned off car and continued to spew out for several minutes.

Sounds like your gas cap may not be on right or is faulty ...and is now heat is forcing the fuel out of your gas tank. If removing and reinstalling the gas cap or even replacing it doesnt work, this is just an idea as to what the problem is. This is a very hazardous driving situation. I would NOT let anyone drive this car at the moment. Call a repair shop that has the ability to tow the vehicle. and expect a price tag somehwere in the range of 600-800 dollars to replace a fuel pump plus towing. Leaking fuel at that rate is not to be taken lightly. In anycase,it could be a fault in the fuel vapor canister, fuel lines clogged or damaged or even a faulty gas cap. I just want you to be safe at all costs...and if towing it ensures it...then do it.

Sounds like you have a bad/blocked vent tube. It is allowing the tank to build up too much pressure.