So does the tank need to be grounded or not? I put a new unit into a tank the prior owner had exchanged. He had put in the original unit. At full, the gage read just over half. When I filled it up, it would only take about 7 gallons. I put some leads on the (TWO) wires that go to the sending unit. With the new unit in my hands, I could watch the gage go full spectrum. Empty to full. I put the new one in,,,,same problem. I took it out again, looked inside,,see nothing for it to hang up on. I have now measured the old unit thoroughly, but haven't had a chance to measure the tank yet. There are two wires coming out of the same harness as the two sending unit wires. They are butt connected together. It looks as though they had been painted green at some point. I guess I'm asking if they might be a ground for the tank, and should I affix one to the tank. Thanx in advance for any responses.