I have a 1986 Pontiac Firebird with the 2.8 V6. I have had the gas tank replaced hoping to have the problem rectified, yet no avail. I have gone through 4 gas caps and all have leaked. An interesting problem I noted is that the threats on the aftermarket caps are too deep and have to be trimmed in order to fit the treads on the filler neck.

I have lessened the amount of gas leaking by using non-gas soluble liquid gasket on the gas cap, yet the car still consistently leaks with a 3/4 full or higher tank of gas when making right turns and accelerating at anything more than a snails pace.

Have any other owners run into this and if so how was it corrected?

Thanks,
Greg

 

You must have the wrong gas cap on the car then.

 

I have the same problem on my 84 TA. I have tried gas caps from dealer and no help. I really don't want to change the tank and it still have same problem.
I have owned this car since 1991.

 

Is the little flap in the fuel filler tube intact.That should keep most of it from sloshing out.

 

YES the flap is there.