Joe
I don't know your tractor so my comments are more generic and based upon the WSM.
The WSM shows there are different wiring systems, some with OPC i.e. Operator Presence Controller.
Having a cab changes the complexity of the wiring.
Do you have a cab.?
When I read your post, battery and cable issues jump to the top. You say only clicks from the fuel solenoid. That just screams poor electrical supply. Later in your post you talk about jumping the starter.
Could you please post photos of the top of your battery, the cables and finally where the negative cable attaches to the frame.
I am going to post some photos from previous owner problems to give you an idea of what I am suspecting.
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Can you provide the part number of the engine stop solenoid you bought and is it a Kubota part or other.
Does the stop solenoid have 3 electrical terminals or two.
Can you verify fuel is being delivered to the injection pump?
If you remove the engine stop solenoid from the engine, do things change when you crank the engine by jumping the starter?
You state you can spin the engine and usually this means the battery and cables are OK but I would like to double check. When you jump the starter is the engine turning over. some owners do the jump improperly and only the starter spins.
When you say "lights work," if the headlights are on and you jump the starter do the lights dim significantly.
The starter wiring diagram shows a diode between the two stop solenoid terminals. There is also an oil pressure switch tied into the SS.
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I I am not trying to question your knowledge and skills but playing doctor at a distance is a challenge and some terms mean different things to different people.
Dave