Having an issue with my fuel tank, and I'm not sure of where to even start the diagnostics. When I take off my gas cap, there's a huge pressure release, which seems to be fairly common. However when filling my tank, the pressure builds so much that it keeps shooting the pump handle back, as in what happens when your tank is full. It takes me 3x as long to fill my tank because every 5 seconds I have to stop and start filling again. Anyone have any suggestions as to how I can release some of the pressure? When I turn the car off, I can hear what sounds like something boiling near the distributor too, not sure if it could be related or not? I'm going camping next week so I'm not very interested in dying in a fiery IROC explosion. Not yet at least

 

That sounds like a vapor recovery issue with the tank. When the cap is off and the nozzle is in, there is nothing to let pressure build. There should be a smaller tube inside the filler neck to let the vapors come back up while fuel is going down. That may be blocked, but I don't think there is a way to even look at it. You may just need a new tank

 

I was hoping that wouldn't be the answer. Are there any issues that could come with that kind of pressure while driving? Could it build high enough to burst the tank?

 

Try disconnecting the relief valve first. It'll vent vapors, but it's a diagnostic step, not a permanent solution. If the problem goes away, look into the valve.

 

I'm not at home right now and the pics I see on here are tough to tell from. Is the valve on top of the tank, and only accessible by dropping it?

 

No, it's mounted to the bracket in front of the axle on the body, where all the hard lines transistion to soft lines, and the brake line ends. It just snaps into the bracket, but be forwarned, the clips will probably break when you go to remove it. The plastic gets very brittle with age.

 

Found a thread from last year saying that there still aren't replacements available. Do you know if that's still true? I can't find any online or in the forums

 

It's long discontinued with no direct aftermarket replacement. Some have had good luck taking the valve apart and cleaning out the gunk. I didn't really feel like trying to pry apart a plastic part well on it's way to returning to the earth as dust, so I just scrubbed the thing with soap and water as best as possible and flushed it repeatedly with warm/soapy water. All kinds of trash came out of that valve. I'd start by simply disconnecting it to see if it's even related to the problem, and then move on to trying to clean it or finding a viable replacement.

 

Will do. So there's no harm in removing it and taking the car for a drive? Or should I only run it for a minute or 2? I can't imagine it doing anything more than just .. venting

 

Shouldn't be an issue. All the valve does is act as an emergency pressure relief. It'll vent if there's an under pressure or over pressure condition. The rest of the time, vapors should vent to the charcoal can, or be directed into the intake manifold to be burned.

 

https://www.thirdgen.org/forums/tech...high-tank.html

 

Something strange happened today that seems related to this thread but not sure. It was hot today over 90. Went to get gas and cap wouldnt unscrew. Very tight so it just clicked. I had to pinch it and turn hard and it finally released. I filled with gas and went to put gas cap back on and wouldnt screw in as it was tight. Just clicked. I tried pinching it and screwing it in but could only get it about half way. Drove fine but when I got home after an hour drive I got out and smelled strong gas smell. Found the fumes were coming around the gas cap which didnt surprise me but what concerned me was the sound of the fuel bubbling in the tank. I felt the tank it it felt warm to me. It has the shield in place but does the tank usually get warm enough to boil the fuel. Was it boiling because it was venting from the cap? Do I just need to replace the cap to get pressure in the tank?

 

Anyone have the issue I posted above? After the car sat in the garage overnight the gas cap threads out and in just fine. It seems when it gets hot it is tight and wont thread well? If the cap doesnt seal will that cause the fuel to bubble in the tank?

 

I'm obviously not an expert, but I'd say you have a similar pressure issue to me, but just far worse. I don't see any reason why the cap wouldn't tighten though, as that would take some serious pressure. Have you checked the valve that Drew mentioned? I haven't had a chance to look at mine, but I'm willing to bet it's gummed up