well my fuel gauge was about 1/4 tank during a drive when suddenly i passed a rough bump on the street and the fuel gauge began to come up, up, up until full.

Now no matter how much gas i have it always marks a full tank when car on,

the gauge goes down empty when car off and then full when key turned acc as normal, so the cluster is doing good.

may be the fuel sender unit???

thanks!!!

I have read in the past that this happens when the sender is bad. The float may also be stuck or messed up on the sender as well.

Lucky! I wish my car would magically be full of gas every time I start it up.
Sorry, I wish I had something to contribute to help you out...Freelancer may be on to something