With the old Ford fuel sending unit not working properly, I had to order an aftermarket unit to use on the FMT's fuel tank. Only problem is I don't want to have to cut another hole in the fuel tank, especially since the tank still has fuel inside. The only other option is to modify the old sending unit yet again to accommodate the new sending unit. Really what I'm doing is salvaging the base and somehow merging the two together. What this entailed was cutting out the old stuff, including the fuel line tubes from the base. One of the tubes will be used as the pickup tube but the other one is not needed. I ended up using a rotary tool to cut out the metal around the fuel tube and also a large hole around where the new sending unit base will be mounted to. I drilled holes around this large hole for the mounting holes on the new sending unit. I also drilled another large hole off center to accommodate the fuel tube. After getting the base hole set up for the new sending unit I had to weld a plug over the remaining hole from where the other fuel tube was. Once that was welded shut I ground down the slag to smooth things out then took the fuel tube we'll be using and clocked its output line based on where the sending unit base sat on the fuel tank. This was so when the base is secured, the output would be pointing forward and not backward or to the side too much. Once that was established I welded the fuel tube in place using the surrounding metal that I cut out with the tube as an attachment point so the welding won't damage the fuel tube itself. With the plug in and the fuel tube welded in place I was able to bolt down the new sending unit on our modified base, using small nuts and bolts that came with the sending unit. From there I took the wiring harness from the old sending unit and crimped a fork terminal and secured it to one of the mounting bolts on the new sending unit and a ring terminal on the positive side which was secured to the terminal on the sending unit. This allowed me to test out the sending unit with out multi guage cluster to see how to calibrate the gauge to the sending unit. After playing around with the gauge settings I ended up finding that the best setting that was available on the gauge was one where full reads around 63% full and 0% when the float is around the 1/3 to 1/4 full level. While this is pretty bootleg in its operation, it's kind of idiot proof. When the tank is full its going to read in that 60% ish range for a while. As the level goes down the number will go down and by the time the gauge reads 0%, letting you know its time to fill up, you can still rest easy knowing you still have about 1/3 to 1/4 tank of reserve fuel to get to the petrol station to refuel. There's really no risk of running dry when the gauge hits 0 at this point. With that taken care of, I was able to go ahead and remount the new sending unit assembly back into the tank and remount the tank so later on I can start dumping fuel into the thing and real time test the gauge as well as get the engine back up so we can start really putting this truck on the road for more extensive testing.
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May 2023
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