Getting a lot of pressure build up in the gas tank. Car is sitting in my garage with the plenum, runners, and fuel injectors/runners off, and enough pressure builds up to force gas backwards up through the fuel lines. Turn the cap, and get a hiss. What is the issue. Why won't the pressure go to the charcoal canister? I pulled the canister tonite, and it looks pretty non-serviceable. Can't tell if it is just full and no good, or what. I put the cap on to see if it builds pressure tomorrow.

What do I need to do, or should I just put a vented fuel cap on, junk the evap system, and call it even. I hate to vent gas, and waste almost $3 a gallon liquid gold, but I don't feel like spending a dozen hours fixing something......nor hundreds of bucks buying parts......

 

Removeing the cap will let off pressure and keep gas from comming back up thru the fuel lines. Also, Get under your car in the back by the tank on the drivers side and check the vent to be sure it's not stopped up.