How do you fix a Gas cap release on a 1991 Mazda miata?

Answer 1

Either one of three is usually occurring:

1. The spring is old/broken that pops up the lid.

2. The lid's hinge is stuck (rare)

3. The release pin is stuck/broken.

To diagnose 3, have one person hold the fuel lid release lever up inside the car. Then attempt to lift the lid. If you are unable to pry it, or risk scratching the car, clean the lid, and use a suction cup to lift it. If it does not lift, then you know that the release pin isn't working. You can remove the release cable from inside the trunk/boot if needed.

Typically, a stuck hinge, or a sticky release pic can be restored with a little silicone crease.

If the spring is broken or loose, you will just have to find a replacement.