Last night I stopped for fuel and ended up spilling a bunch of gas on the ground. I shut the car off and put about 6 gallons in the tank. I left the cap loose because I wanted to put some gas dry in since it is cold here and my car is sitting for several weeks at a time. I did not "top it off" or over fill the tank. I went in to pay and forgot the gas dry. I looked down at the cap and gas was coming back out of the filler neck and onto the ground. 1-Why was it doing this? The car has ran poorly a couple times and I assumed it was bad gas because when I put more in it would then run fine. 2-Could just removing the cap and replacing it have corrected this? When I put the engine in this summer I plugged the return line to the tank. 3-Should this be vented instead? It does hiss some when the cap is removed. I am running a holley street mechanical fuel pump. The runs great usually and was running fine before and after I stopped for gas.

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350 Vortec, forged flat-tops, CompCams XE268, Edlebrock RPM, Holley 3310, TH350 w/Holeshot 2400, 3.23 posi, Heddman shorties, HEI

 

erik boy, i did the same with my previous camaro (plugging the return line) and never got gas out of the fuel cap no matter how much i've put on.
but your hissing sound comes from a negative relief valve that's stuck, simply go under your car(just ahead of the aft/left wheel) follow the fuel lines up-flow of the filter and you will see a white plastic thing connected to a rubber hose, its easy removal dismantel-it (very easy) and clean it with hot water and soup put it all back together and hissing is gone. (i did it myself)

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What kind of "soup" are you using to clean it?

Sorry, just being an *** .



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'83 HOmaro--doesn't run
'92 Bird--burnt to a crisp
'78 T/A 400--fast, Burt Reynold's style
'83 Buick LeSabre--the Ghetto Cruiser

"Without evil there can be no good, so it must be good to be evil some time!"