Onan 3.6 won't crank

On the wiring diagram it has the jack pin out where you could see if you have 12 volts at the control board. It is kind of strange, no fuse, you might need the control board. If it was mine I'd be inclined when all figured out to add a fuse.

The Install Manual there for Spec "R" does include a wiring diagram and it does have one difference compared to all the other earlier-Spec manuals I've downloaded: IT DOESN'T SHOW ANY FUSES.

Really I can't recall the last time I saw a product that connects DIRECTLY to a vehicle battery that didn't have a fuse internal or in-line for component and fire protection.
Very strange. Very stupid, IMO.

This url will take you to a page for your unit, there is a download section where manuals are, in the operator manual section 4 page 21 there appears to only be an AC breaker. This manual does not have a wiring diagram unfortunately. I did find another manual with a wiring diagram, it showed 12 volts going directly to control board, I'll find it again and post link however while it's for a 3.6 not exactly the same model.


https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi4x9r9oKT6AhVIhIkEHY01CR8QFnoECBAQAQ&url=https%3A%2F%2Fwww.coloradostandby.com%2Fcummins-onan-3-6-ky-fa-26120-rv-or-commercial-generator-set-rv-qg-3600-lp&usg=AOvVaw2EMtr_TesUTaxXFTnvSi-u

Ok here's the label:

There is more than one type 3.6, the full model number would help.

Spec: R
SN: B170148513

need to know "spec" letter, and serial no. of gen to know which control system you have. In any case, oil level has NO EFFECT on starter and cranking operation. Older spec units did have low oil level cut out switch, but did not prevent starter operation. And...these units dont hold much oil (imho) and should be run at full crankcase level for maximum engine protection. Lots of useful info on internet,,,lots of B.S. too

This is probably a stretch but the last thing my friend did before having this problem was change the oil. There are YouTubes that claim filling the oil up to the 'FULL' mark on the stick can cause the genny to mysteriously shut off after a few minutes. I'm wondering if 'too full' could also prevent cranking?
I'm doubting this is my problem since the start switch has no light at all & I assume an oil level interlock would let the switch light up & allow cranking.

Thanks for the suggestions.
I still want to check the simplest things first. The fuse that's shown on the wiring diagram. That I can't find on the unit.

bear in mind that Onan start/stop control switches are switching grounds, not batt voltage. Sounds like your start solenoid and starter are ok since it cranks when you jump 12v to solenoid start solenoid. Since neither switch will activate starter, I would suspect bad control board or ground circuit to control board. Also, disconnect remote panel wire harness, and try it at generator control. If it cranks now, you have a shorted harness on stop circuit, as the stop circuit overrides start circuit.