Ok I grounded the wire from the sending unit the gauge worked. I can see and get to the retaining ring holding the sending unit in from the access hole in the trunk. I can not get it to turn I tryed the hammer & screw driver trick it wouldn't budge But did not hit it very hard. All of the tools for removing it are very expensive does anyone have a free or cheap way to loosen the retaining ring. how do I check it for good ground?