Onan genarator will not crank

If you are jumping across the starter solenoid and it cranks. If it was one of my fords back in the day I would think the solenoid is bad.

operators manual, page 19, starts troubleshooting, reset circuit breaker page 8
http://www.joshwakefield.com/xplorer/onan-microquiet-4000.pdf

Installation manual, fuse, Wiring,
https://manuals.heartlandowners.org/manuals/Electrical/Generator/Onan%204000/ONAN%20Installation%20Manual%204000.pdf
video links below
https://www.youtube.com/watch?v=R3NiRyeCf14
https://www.youtube.com/watch?v=PTo-NkoKndg
https://www.youtube.com/watch?v=ndyWd-R8Psk
https://www.youtube.com/watch?v=qYy0nbRs7Ts
https://www.youtube.com/watch?v=QIFOeECaYHA
https://www.youtube.com/watch?v=Yfz3dA-bic4

This link below is very interesting (oil level shuts down)
https://www.youtube.com/watch?v=vzXDlln8aUw

Odds are that the ignition switch or wires are giving you the grief.
Thee unit will probably be getting spark power through the starter solenoid (look for a wire there) but when the solenoid is not activated, there will be no ignition power.
Take your time and trace it down.
You'll get it.
Cheerfuls!

idk if the first post posted so im going to try again. trace your wires throu the firewall and see where they go. then pull that relay and test for live wires. if the ciruit is hot and the relay isnt pushing anything. you found your problem. also check headlight relay. may run ignition switch.

If the problem is the starter won't crank the engine over, check the small wire at the solenoid (the one from the ignition switch). It should have power when the key is held in crank. If no power there, trace the signal back to the ignition switch-check the neutral safety switch-at the clutch pedal-or the park/neutral switch on the transmission, if automatic. Check if the ignition switch has power out of it on the start wire with key in crank. Use a voltmeter or testlight for checking.

First thing to check would be the starter solenoid-mounted on the starter. In the starting circuit, that is the most high use/high wear item. A tech would wait for the no start condition, then check the solenoid wire for power when key is held in the cranking position. If power is there, it indicates a faulty solenoid. If no power, trace the signal back to the ignition switch-from solenoid to starter relay to clutch switch to ignition switch.
There are contact points (plates, really) inside the solenoid that become pitted and burned from use, and eventually wear down or out.

See if you have power at the solenoid wire when key is held in crank position. If you do, then battery connections are not tight, or you maybe got a defective starter or solenoid. If no power when key is held in cranking position, trace the start circuit backward from the starter solenoid to the ignition switch-starter relay and the neutral safety switch are in that path. Check for power in the start wire leaving the ignition switch, by backprobing with a voltmeter or testlight the ignition switch harness connector.

Nice descriptive statement. Too bad it can't be flushed and forgotten!

Some testing will have to be done to find all the problems. A new battery and starter is a good start. It will make finding the no crank problem a lot simpler and hopefully not expensive. You could check for power to the starter solenoid when key is held in cranking position. If you have power there, check grounds and battery and starter cable connections-starter is not getting power from the battery. If no power on the solenoid wire, you will have to trace the path from the ignition switch to the solenoid to find the problem. I hope you have a wiring diagram for the start circuit, You said you checked fuses. Did you check if they all have power with key on? Something like a fusible link (if your car has them) could blow out and cut power to fused circuits.
Well, good luck. Post back if you find anything or need more help "polishing".

you never mentioned if you have power from the switch, check for power in and out of switch with volt ohm meter, then trace wiring to starter

I am guessing that it may be the neutral safety switch

Check all your fuses..It maybe just your fuse for the ignition...which in fact turns your starter over.... And yes your starter is good, if it tries to crank when you jump it..Now if your fuses are good, then yea your problem mat be the ignition switch itself....But check all your fuses first...Goodluck...