when turning on the headlights, we hit a pot hole, the gas Gage gos south and the dash lights go dim.sometimes just starting the engine the fuel Gage goes south (too E) we took it too a dealer and it wouldn't do it for them and wen the fuel tank is full it wont do it either,im perplexed and cant get under it too look at the tank. any ideas ? every time i take it too someone they cant find anything wrong.