I took out the 6 small bolts that look like it keeps the sending unit in place, no movement of the sending unit, how do you lift the sending unit out. It has never really worked, always shows a 1/2 tank when empty. Thanks
There is a cork gasket that likely has sealant on it or is just stuck. You will need to pry it out gently. Some cars had the sender installed out of phase, i.e. with the float arm clocked so that it bound on the tank side. You can test the system easily by grounding the wire to the gauge, if it reads full the gauge is OK. You can then test the sending unit with an Ohm meter as you sweep the float arm through its arc.
You can then bend the arm to allow it to read semi-properly. As the tank is a trapezoidal shape the F to E will always be skewed. I think it is more important to have the E reading correct. If you set the arm for this the gauge will read "full" longer but from 1/2 tank on you will have a good indication so long as you remember that the shape of the tank means that fuel level is going down faster from that point than from "F" to 1/2 tank.