Why do the fuel gage go from empty to full when I start the car? on 2004 Buick LeSabre

after about 5 or 10 minutes it goes back to empty. Sometimes it will come back up to half full or more then drop back to empty or up to full.

1 answer
THERE IS PROB A RESISTANCE ISSUE IN THE FUEL SENDING UNIT. IM NOT SURE IF THE SENDING UNIT IS SOLD SEPERATELY OR NO CK WITH YOUR LOCAL PARTS DIST.