My new sender was sticking and my wires were proper. The float on my
NEW sender was sticking at 3/4 when I filled the tank and 1/2 when I drove. Since it is a plastic float on a metal wire, I pulled the sender and gently rotated the sender to make the float move. After about 15 minutes the float moved easily at low inversion angles. Solder/flux on the wires or a burr inside the plastic float? Sometimes you have to get a touch of wear to get things to settle into place. I followed KISS(Keep It Simple Stupid guidelines) and attacked the simple procedures first. IMHO Why tear apart the motor when you only need a new spark plug & valve adjust? Was your old sender just worn out? Dash gages are not precision instruments due to cost constraints. I did not want to start chasing electrical issues when my old sender died from non-movement when the car was held prisoner at the Porsche Stalag
(PS Racing in Burbank). Best of luck.