i can hear a blump noise comming from my gas tank. It is similar to the soud u get if u dented a bottle and blowed into it. Im sure its comming from the gas tank. Somtimes when i hear it i unscrew the gas cap just to see what happens, and it blumps a little bit more but not after the pressure is let out. Anyone else get this noise? whats wrong? Im thinking maybe the cap isnt allowing air in. The cap doesnt look stock..its grey with an "S" on it. can someone describe what the stock cap looks like?

 

My 86 does the same thing, there's a little white valve attached to a hose that goes into the gas tank, I think it is a vacuum relief valve, mounted to the body by the rear suspension. It maybe blocked or stuck.

 

hey thanks a lot, i'll check it out tomorrow