Join Date: Mar 2004
Location: Valley Center, CA
Re: Excessive gas tank pressure
I have been working on the same problem. I have 2 new GM gas caps, both work the same. They have a 2 way valve that allows air in as gas is used, and they vent out excessive pressure. You can check by blowing hard on the center hole inside of the cap. I am trying to determine that release pressure in P.S.I. I guess about 5 psi. But it is not low enough because it causes the car to cut out a little under load when it pressurizes. The valve can be moved to one side with a small nail and it will prevent pressure build up, but will also allow gas fumes to escape-not good. So I am working on a way to lower the release pressure in the valve.
69 SS350 ZL-2 4 speed, original paint, unrestored -SOLD
1972 AMX 401ci, 4 speed, cowl induction, console, gauges, posi, A/C, unrestored original