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Q: Fuel gauge dropped dramatically and the gas tank looked like it was suctioned in because of a vacuum

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While driving my truck at highway speeds, I noticed that the fuel gauge started to drop very quickly, almost half a tank in about 7 miles. The engine seemed to be running fine, no sputtering of anything. I pulled over to check if it was leaking fuel when I noticed that the fuel tank itself had suctioned inward as if there was a vacuum being put on it. I opened the fuel filler door and depressed the little door inside the neck which let air back into the tank and caused it to look normal again? Any ideas?
My car has an automatic transmission.

Hi there, thanks for writing in your question and the details of your situation. Based off your information, I’d like to mention that the fuel fill tube has a fresh air inlet that should prevent this from happening. Either an inlet valve may be damaged, or a the fuel fill tube is defective. I’d recommend having one of our certified mechanics inspect the fuel fill tube to see if it is binding and needs replaced.

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