My buddy is having a fuel gauge problem it shows full when its empty did checked the grounds they are all good power to the gauge too.What it would be wrong?

 

Most likely it would be the sending unit, either is bad or you have got a bad floater in the sending unit. The floaters are known to get holes in them thus giving wrong readings. I recently replaced the sending unit in my truck in the front tank and the hole problem was a bad floater, but since I had the truck bed off I also replaced the rear tank unit.

 

maybe your floater is stuck, causing it to remain afloat even when the gas level is low.