My gas tank in both my 96 Tracker 2 door and 94 Sidekick 4 door pressurize. I was wondering if they were supposed to. I'm use to a small hiss when I take the cap off other vehicles but both the Tracker and Sidekick put a lot of vapors out when I remove the cap. The Sidekick gas tank actually made a thump sound the other night from it going back to the shape it should have been.

Too dangerous for me if. If I was to be offroading and snagged the tank bad, sparks from dragging on rocks + vapors = boom.

It's normal.

mine also pressurizes. i have learned to release the gas cap before working on the fuel system.
i don't think i'ts developing the kind of pressures you indicate.
mabe your gas cap is bad(i think there is a relief valve in it?).

mine also pressurizes. i have learned to release the gas cap before working on the fuel system.
i don't think i'ts developing the kind of pressures you indicate.
mabe your gas cap is bad(i think there is a relief valve in it?).

From what I recall, the gas cap is set up to let air in, but not let air/fumes out.

My gas tank in both my 96 Tracker 2 door and 94 Sidekick 4 door pressurize. I was wondering if they were supposed to. I'm use to a small hiss when I take the cap off other vehicles but both the Tracker and Sidekick put a lot of vapors out when I remove the cap. The Sidekick gas tank actually made a thump sound the other night from it going back to the shape it should have been.

Too dangerous for me if. If I was to be offroading and snagged the tank bad, sparks from dragging on rocks + vapors = boom.

Pressurized or unpressurized, there WILL be vapors in the tank - I can suggest a little experiment if you don't believe - so let's assume your tank is not pressurized, you're off roading, and snag the tank bad, sparks from dragging on rocks + vapors will still = boom.

Emission control requirements are what dictate that the tanks be "sealed" systems - no the caps aren't vented - there should be a vapor recirculation system with a charcoal canister and a purge valve that is controlled by the ECU to release the vapors to the intake manifold so that they are burned in the engine, make sure yours is functional.

your tank should not pressurize enough to expand the tank and you should hear pressure release when you loosen the gas cap that is normal