Ok, before you go at this the wrong way, first take out the float switch. Have you done that? It is a long brass rod, with two floats on it. Look at TM 5-6115-615-12, figure 3-14, page 3-30. See if the lower float moves up and down freely. Then check if it has the three magnets still are in the float. Use a screwdriver tip to find the magnets. Dont dig for them, just hold the screwdriver tip close to the float in several places. Then test for continuity, between pins A and B, with a multimeter. Move the top float up and down its full range to see if you open and close the contacts. Then try the bottom float. See if it opens or closes when you move the float. Repeat for pins C and D. I forget what pins go to what float, so just try it. If the contacts open and close properly when you move the floats up and down, then you might just try and change K-4 relay. Its the relay that shuts the engine off, when the bottom float sends a signal that the tank is dry.