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A stuck gas cap isn’t the most dangerous or difficult car problem to have, but it’s one of the most frustrating. You can’t put gas in your gas tank if you can’t get the gas cap to come off. It seems improbable that the cap would just get stuck, but it does happen. When it does, you’ll want to call a mechanic rather than trying to force it open.
The gas cap and gas tank is a very straightforward system. The gas cap has outward thread (like a bolt), while the head of the gas tank has inward-facing threading (like a nut). The gas cap screws into the top of the gas tank, which keeps the gas securely in the tank, and keeps debris from contaminating your fuel tank. When you are at the gas station and ready to fill up, the gas cap easily unscrews so that you can top off your fuel tank.
There are three common reasons why your gas cap might get stuck on:
Vacuum sealed: Under certain conditions, your gas tank can create a vacuum-like seal around the gas cap, which seals the cap tight. This vacuum situation occurs when the pressure inside the gas tank changes, which can happen due to extreme changes in weather or altitude, among other things. This high pressure situation creates a vacuum seal that makes it nearly impossible to unscrew your gas cap.
Poorly threaded cap: Be it out of haste or simply not noticing, sometimes people screw on their gas caps incorrectly. If the thread does not match up, you can sometimes force the cap on, just like you can force a glass jar lid on even when you’re not screwing it on correctly. If this happens with your gas cap, it can be extremely difficult to get off.
Debris in the threading: If dirt, leaves, or any other form of debris contaminates the gas cap and gas tank threading, the cap can easily get stuck. This debris can get trapped in the threading, creating extra pressure and friction, making the cap resist that much more when you try to unscrew it.
A top-rated mobile mechanic will come to your home or office to determine the cause of the gas cap that won’t open, and will then provide a detailed inspection report that includes the scope and cost of the necessary repairs.
A mechanic will use a specialty wrench to help unscrew the gas cap. After the cap is off, the mechanic will determine what the cause of the problem was, and repair or replace any damaged parts.
If you can’t get your gas cap off, you have a limited distance that you can drive. You never know when you’ll need your vehicle, so it’s never a good idea to be stuck with a finite number of miles. You should have your gas cap fixed the moment you notice that it’s stuck, so that you can rely on your car anytime that you need it.