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JDM '94 gen3 turbo
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39 Posts
Discussion Starter · #1 ·
Hey guys,

I've found that if I drive my car for more than like 10 minutes, it becomes insanely hard to take my fuel cap off. I'm completely incapable of doing so by hand, and I end up having to use vicegrips/pliers or something that can give me leverage on the cap in order to do so. Its bad enough that I've resorted to just always making sure that do my fill-ups right after I leave my apartment.

When I DO manage to get it off using pliers, there is a huge whoosh of pressure escaping from the tank. I'm assuming this pressure is pressing the cap into the threads, and making it almost impossible to turn by hand.

This doesn't feel normal. I'd expect there to be some pressure, but not to the extent my car seems to have. Is this a common issue on these cars, or is mine 'special'? Any way to prevent/fix it?
 

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328 Posts
Maybe it's time to replace the gas cap?

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Step 1: Inspect the gas cap for damage
. Once the gas cap is removed from the vehicle either by yourself or a professional mechanic, inspect the a few individual components that may have caused the gas cap to stick or spin freely without being able to come off.

  • The pressure relief valve: This part is located inside the gas cap and is what allows small amounts of pressure to be released from the cap in cases where the tank is building excessive pressure. If the valve is stuck, it can cause excessive pressure to build up inside the fuel cell and make it difficult to remove.
No idea if it's a common issue. One of the first things I did when I got my MR2 is replace the gas cap just because the old one was... old.
 

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Super Moderator
91t gen5
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6,845 Posts
It sounds like you're pulling a vacuum on your tank. Have you removed or changed the charcoal canister setup? There is a vent valve that runs to the bottom of the car next the fuel filter you could check that it isn't blocked but I'm betting you vacuum lines aren't right.
 

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JDM '94 gen3 turbo
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39 Posts
Discussion Starter · #4 ·
I suppose I could probably user a new gas cap regardless of if its the issue or not. Mine does have that "27 year old plastic" feel to it haha.

I haven't touched my canister, but that doesn't mean it hasn't been messed with previously. I'll see what its current status is. I found this thread from 10 yrs ago that helps me understand what that it and why it might be happening.

As far as vacuum lines not being right, I wouldn't be surprised at all. I already had to fix one vacuum line issue leftover from the previous owner. I guess I'll look into that as well.
 

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Super Moderator
91t gen5
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6,845 Posts
As a test you could remove and cap the vacuum lines going to the engine from the charcoal canister.
 
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