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Another Onan "won't start" Thread...


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  #1  
Old 04-11-2018, 07:11:56 PM
Frankshay Frankshay is offline
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Default Another Onan "won't start" Thread...

Hi Everyone,

Model 2.8KV FA26100G S/N E990911263 in a camper we've had a few years now. I bypassed the oil level switch a couple of years ago to solve an intermittent failure issue. The unit has been working great! Up until I went to start it the other day that is. I changed the oil at the end of the season last year, ran some stabilized fuel through it and let it sit for the winter. This spring I went to start it (after getting the camper going) and it cranked over quickly as usual, popped once or twice, then did nothing after that.

I gave it a couple shots of ether, thinking that would help but no joy. After fooling around some more I removed the spark plug and it was a bit grungy so I cleaned it up, but no spark when holding the plug against an engine ground. I've looked for spark with a new plug but still nothing. Suspecting the coil I measured primary and secondary resistances which were pretty close to nominal. I'm wondering if I have to go deeper inside to investigate the magneto? Can coils weaken under load even with good nominal resistance readings? I experienced weak sparks with this unit before but it has been working fine.

Can anyone offer any thoughts on how to best proceed?

Many thanks,
Frank

Also: am I correct in thinking this unit does not have points anywhere? I don't really understand how the magneto operates. I always thought it was non-contact but perhaps I'm wrong.
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  #2  
Old 04-11-2018, 07:47:20 PM
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Billy J Shafer Billy J Shafer is online now
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Default Re: [Onan] Another "won't start" Thread...

Give us time to look things up. But I believe that model has a low oil level switch. They were such a problem Onan stopped using them. Does not have points.
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Old 04-12-2018, 09:15:19 AM
Frankshay Frankshay is offline
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Default Re: [Onan] Another "won't start" Thread...

Hi Billy,

Yes it has the switch but I bypassed it earlier to make the unit more reliable.

I'm going to retest the coil, I don't think I looked for continuity between primary and secondary leads. (There shouldn't be any, right?)

I've remeasured coil resistances and get:

primary to ground: ~.5 ohm
Secondary to ground: ~1052 ohm
primary to secondary: ~1053

Do these numbers make sense? I guess there is a path between primary/secondary via the ground. Measurements taken with coil removed.

thanks
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Old 04-12-2018, 10:01:13 AM
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Default Re: Another Onan "won't start" Thread...

Let me get the book out and check. Phone is going crazy this morning.
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Old 04-13-2018, 02:02:20 PM
Frankshay Frankshay is offline
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Default Re: Another Onan "won't start" Thread...

I reinstalled the coil with new spark plug and noted voltage at the primary side when cranking: -2.x volts! Meter had + lead on coil wire and - lead grounded. I have no idea what that means... Anyone?
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Old 04-13-2018, 03:24:16 PM
Frankshay Frankshay is offline
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Default Re: Another Onan "won't start" Thread...

Also, I forgot to add that it shows the same symptoms with the plug from the inside panel disconnected. (I was hoping the inside start/stop switch had a fault.)
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Old 04-16-2018, 03:55:57 PM
Frankshay Frankshay is offline
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Default Re: Another Onan "won't start" Thread...

I've been using a service manual found online http://www.twinslan.net/~n0nas/manua...0(03-1991).pdf to trouble-shoot. One of the items that's confusing me is that the wiring diagram and descriptions talk about some physical relays K1, k2, k3 all with various purposes. The problem is that all I have is the start relay (solenoid) and the others are nowhere to be found. In fact all the wires seem to run through a white box underneath the unit (mounted onto the frame).

Onan white box by Frank, on Flickr



Close-up with ID #:


Onan white box ID by Frank, on Flickr


Has anybody stumbled across this situation before?

(thanks)

I'm pretty sure the box is a voltage regulator but the question is: could this be grounding out the ignition coil somehow?

The other question is - how do I find a better service manual?

Thanks again
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Old 04-16-2018, 04:52:54 PM
Wayne 440 Wayne 440 is offline
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Default Re: Another Onan "won't start" Thread...

That manual is for spec A and B - your set is spec G.

---------- Post added at 03:52:54 PM ---------- Previous post was at 03:51:42 PM ----------

This may be somewhat closer to the correct manual.

http://www.twinslan.net/~n0nas/manua...0(09-2009).pdf
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Old 04-16-2018, 05:34:54 PM
Frankshay Frankshay is offline
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Default Re: Another Onan "won't start" Thread...

Ah yes, you're right. I didn't see that - it sure explains the missing parts!

Thanks very much
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Old 04-17-2018, 02:29:12 PM
Frankshay Frankshay is offline
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Default Re: Another Onan "won't start" Thread...

Troubleshooting continues...

I decided to replace the coil. My initial measurements showed the primary coil resistance was a little low and secondary was spot on. I've rechecked with another meter and it reads even lower on the primary side. I've had a weak spark in the past so this seems it may be part of the problem.

I've also done some checking on the voltage regulator. The manual (thanks Wayne 440) says when performing field voltage tests: "If the genset cranks but will not run, check to see that battery voltage is supplied to the voltage regulator (pin 7) and ground during startup. If (so) ...there should also be battery voltage between pin 9 and ground. If no voltage at pin 9, replace the voltage regulator and retest."

Pin 7 shows voltage to ground but pin 9 is open and this genset cranks but won't start. Before replacing this expensive part though I'd like to know if this makes sense. Why would the voltage regulator prevent the genset from even firing? If anyone can add insight I'd appreciate it!
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