Why do so many people put those cheap inline filters on and pull out the OE filter? It catches water in the cup which in lines don't and there not expensive. Like $5 to 7 at a local parts store? I got the ones I have off rockauto for like $3.
But anyway , hope they didn't monkey with that injection pump. These are gravity fed. That pump is very reliable and expensive to fix or rebuild.
$500 will buy you a lot of parts for a tractor that doesn't sound like it really needs anything ? Just bleed the screws till the all flow fuel starting at the side closet to the tank. All 3 screws, including the one on the pump. Try starting it with a good battery, maybe even with jumper cables on your running truck. Use the compression release to increase the speed of motor. Then crack the lines at the injectors if you can't get it to crank without doing that till you see fuel pulse out and then tighten the lines down.
But I am thinking maybe there is something else wrong. Maybe not to stop it from running but just wrong. Why would anyone with any sense start tearing off electrical parts and wiring on this tractor after they ran it out of fuel and could not restart it? The only thing the wiring has to do with it is so you can use the key sitting in the seat, you don't even need the key to start it.?