Ohm out the sending unit before and after installing in to
Tank
Better yet
Connect the ohm meter up and watch it as you move the sender into place and start installing the screws
And if it’s going weird then you know precisely at what point it’s getting shorted out and can further trouble shoot
This method works better if there is enough fuel to start floating the sender before the short happens
Because it will read empty with the float dropped down
-s
