1966 Coupe restomod
Hey everyone, I recently got a 66 Mustang coupe and had the seller's mechanic install a new sending unit for the fuel gauge. However when I went to fill up the tank, the gauge only went up to a little past the 1/4 mark. So it's not reading the tank accurately. The gauge clearly works because it moves when I start the car and it did go up after I filled up, but only past the 1/4 mark. I initially thought that maybe I didnt fill the tank all the way, but I confirmed it was full because I could see the gas. Any diagnostic advice?