Sounds like you may have a hole in your float. I had the same thing going on. Pull it out and take it off the rod and inspect it. If may have a small crack usually where it snaps onto the rod. If it is bad go to the wrecking yard and get one out of a older Chevy truck with the tank in the cab. When you put it back on make sure the longer end faces forward so you don't have to do it twice. Good luck...

Steve in Idaho