Late in the season, the fuel sending unit went out on my '95 Prostar. Somebody suggested that it could be fixed. Instead of fixing it, I purchased a new one for $160.00 plus shipping. I left the old one on my work bench....until today.
If you have this type of fuel sending unit, and it is inoperative, it is likely that the magnets have come dislodged from the foam float. It is a simple repair to get you back on the water.
There are three main components: The tube assembly, the circuit board, and the float. To disassemble the unit, remove the two screws at the bottom of the tube and remove the plastic cap. Then unscrew the two nuts at the top of the unit to allow the circuit board to slide out of the tube.
The culprit in my unit were the two magnets that are supposed to be lodged in the foam float. They came out of the float and were resting on the tab at the bottom of the circuit board. I just used some 5 minute epoxy to connect the magnets back into the float. Then I used a fine file to smooth out the repair.
I tested the unit by attaching an ohm meter to the circuit board, then moving the float. You can see in the next pictures that the reading on the guage changes as the float goes from the top (full) toward the bottom (empty).
Reassembly is just the reverse of disassembly. I cleaned everything up with WD-40 first. Just be sure to insert the foam float into the tube before pushing the circuit board all the way to the top or the tab at the bottom of the circuit board will prevent you from inserting the float. Once assembled, I tested the unit again, this time by holding it right side up and upside down. This just verified that the unit is back in action. You can also connect it to the fuel guage wires and (with the key on) turn it up and down to view the fuel guage changing.
Hope this helps somebody else in the future. I sure could have used that $160 some place else. This repair took only about 20 minutes and cost nothing.