The fuel sender gets dirty and no longer registers at the top. Easy fix, clean it.
Remove the sender, under an inspection plate behind the rear passenger seat. Find the plug which is over by the pump and take it out of the car.
If it is the aluminum cylinder type, take the cylinder off the sender. Then carefully clean the sender of any residual oil, rinse it completely. I used clean gasoline. After drying, I also attached my multimeter and watched the resistance change while slowly sliding the sender up and down, verifying that it did change over the entire length of the sender.

To remove the large plastic ring holding the sender in the tank, I use the handles of a regular set of pliers to get a grip.

Klaus
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The more I learn, the more I forget. So why learn?