gas tank gurggle

[jenz]

I am having a gas problem. Not me personally but my van. What happens is this: when it is very hot or when I am driving at high altitudes, above 7000ft there is a very strong gasoline odor and a boiling noise. As if liquid is boiling on a stove. You can actually feel the vibration if you touch door to the gas filler area. If I open the gas cap, pressure will come from the tank for over 10 minutes, thats with it just cracked. If I open it all the way, gas will actually spew out. It takes an extremely long time for the pressure to release completely.

Here are a couple of fixes that we have tried:
1. changed the gas cap, 3 different times, no change.
2. changed the fuel filter, assumed it probably wouldn't do anything but couldn't hurt. No change
3. used a high octane gasoline the last few times I filled up, no change
4. just got it back from the shop and they said that there is a screen on a purge valve that was plugged and they cleaned it. I thought that would be it. I just returned from driving about 40 miles, its 100 degrees out and i live at about 4700 and when I got home i could smell fumes, i cracked the gas cap and tons of pressure and gasoline came out. No change!

The vehicle is a 2000 Rialta which is essentially a eurovan with a winnebago camper.

Any ideas? Anyone out there here of this issue? Any solutions? I am to a point where I am a bit afraid to drive it as I really don't want it to catch on fire and blow up. Please help as I would love to get out of the heat and up into the mtns!