How well do you know Onan?

Jim Blackwood · August 27, 2018, 04:19:29 PM

Got a puzzle here. Onan Microlite 4Kw gasoline fed generator 4KYFA26100G

I've been working on this one for awhile now but I've finally got it to where it will start and run... for as long as the start switch is held down. As soon as I let up it stops. I've held it down long enough to grab the governor arm and hold the speed steady, at a higher speed than it would normally run and it still quits as soon as the start switch is released. I quit doing that when I noticed the starter was beginning to get hot.

The unit is out on the workbench with nothing hooked up except for a battery and fuel line. Is this a function of the external wiring? It does have a remote start panel. Or is it something worse?

I'm pretty darned sure there is not an oil level switch on the motor since I've had the wiring harness completely removed and have had the motor sitting on the end bell for the generator and was not able to see anything that looked remotely like a switch or a wiring connection. So that "easy fix" isn't available. Something else is doing it.

Jim

luvrbus · August 27, 2018, 04:26:11 PM

It is a bad voltage regulator order you a after market regulator Onan charges over 200 bucks for it or it could be a bad slip ring you don't want to go there lol.Go to Flight Systems web there they tell you how to check the regulator and slip ring

eagle19952 · August 27, 2018, 04:32:05 PM

Engine Starts But Stops When Start Switch Is Released

1. Low oil level.
1. Check oil level and add oil if low.
2. Defective low oil level switch.
2. Disconnect low oil level switch and 10-2
check set operation. Replace if defective.
3. No field flash voltage due to: 3a. Check wiring continuity to the brush 9-8
a. Open circuit in wiring. block F1-F2, voltage regulator VR1,
b. Brushes not making good contact control assembly A1 and generator
with slip rings. B1-B2 and Q1-Q2 windings. Check
c. Slip ring surface is rough or pitted. connections of P5 and P6 connectors
on the generator housing.
3b. Check brushes for wear and for contact 9-12
with the slip rings.
3c. Check slip rings
4. Defective generator, control assembly 4. Perform field voltage test. 9-8
A1, or voltage regulator VR1.

http://www.rvwithtito.com/download/Onan4000MaintenanceManual.pdf

Geoff · August 27, 2018, 04:37:27 PM

Circuit board. I have rewired several Onans to work with a simple key start or toggle switch. Like Cliff sez, Onan is a rip off.

eagle19952 · August 27, 2018, 04:44:46 PM

ok

Jim Blackwood · August 27, 2018, 08:05:18 PM

Yeah, I guess that's on for tomorrow. I know the brushes and slip rings are in good shape and the windings are good, I had the thing apart to replace the magneto and checked all that out. In fact I've done a lot more work to this thing than I ever expected to. Story was that the POs ran it out of oil, and that checks out up to a point. Less than 1000hrs on the clock so I wasn't expecting to see a lot of wear. Turned out the balance shaft was broken and the end bushing was worn pretty badly. My guess was that it jumped time and the crank hit it. But I found another new shaft for about $100, made a new bushing and drilled out the crankcase to take it so that was fixed. Put it back in the boy's RV.

But it wouldn't start. Had no spark. Wasn't getting any voltage out of the magneto, so back out it came. Eventually got the flywheel off, a new magneto was about $100. So, got that and installed it. Still no spark but only one part left, the coil was about $100 (noticing a trend here?). Got that, installed it, by then had everything disconnected. Got a weak spark, gapped the plug and decided it might be good enough. Maybe. Didn't look real healthy, seems like they might have sorta wimped out on the ignition. Really weak yellow spark. Checked the magnet, it seemed good, so I measured and calculated the gap which came out to .040". Should be fine. Noticed the key for the flywheel was missing so I made a new one and just to be sure, pulled the armature and confirmed that it was correctly indexed. Also went back and re-checked the indexing of the crank, cam, and balance shaft. All OK.

Decided to check compression, what a letdown. Only 50 psi so got out the leakdown tester and decided the exhaust valve was leaking. Pulled the valve cover and sure enough there was no valve lash. Looked up the spec and was kinda surprised to see it call for only .002" so I set them up a little loose, valve recession being what it is and all. If it could lose .002" in less than 1000 hrs... got 100psi compression and 25% leakdown, not that bad for an engine that hadn't run for years.

Well, I got it to hit but it wouldn't start so I shifted my attention to the carb next. That little shutoff solenoid on the bottom had issues. Probably another $100. I took it apart and cleaned it up instead. Still wasn't working so I pulled off the carb. Now I know good and well that is more than $100, more like $500. Internet says:... Not Rebuildable. So I pulled the bowl off and cleaned it out good. Looked pretty clean aside for some residue. Put it back on and it fired right up. Cool. Except for when I took my hand off the switch. Not so cool. And it oscillates but maybe that'll smooth out once it's running.

In retrospect, the ignition parts might not have been necessary. So that's a couple hundred dollars of unneeded expense. Total so far about $300. Still cheaper than a comparable HF which isn't very comparable and much noisier, but how much more is this gonna take?

Sounds like that module is next. The wiring all looks good and I've greased all the connectors, but it looks like voltage checks are in my future. And probably more money for the module. Too bad I can't trade the coil and magneto for it, electrical parts being non-returnable and whatnot. Seriously I'm getting tired of fighting for every single inch with this thing. What's next? Voltage regulator? Jinx. The old Onan generators were pretty good I think but I'm sort of wondering about these newer ones. I've had cars that took less work. How'd all that happen just from lack of oil is what I'd like to know. Lessee, not enough oil so it runs hot, makes the exhaust valve wear from the excess heat which generates more blowby which infects the electronics and melts the flywheel key. Yep. That oughta do it.

Jim

chessie4905 · August 28, 2018, 04:51:59 AM

I've already had this with vehicles....they fall in love with you and you can't get them out of the shop. At least when you conquer this project, you can set up shop as an Onan specialist.😋

TomC · August 28, 2018, 06:23:05 AM

Get rid of that gasoline Onan. I had a 6.5 Emerald III commercial on my truck. Even though the first one lasted 12,000hrs, it was constant maintenance and a pain having to get gasoline on a Diesel truck.
Take my advice, get a good used Diesel generator-you'll be much happier. Good Luck, TomC

luvrbus · August 28, 2018, 06:40:23 AM

They are not that bad of a generator,the CARB compliance carburetor sucks,i found out you can remove the knob and set the carb or remove the jet and spray cleaner in it ,the biggest down fall is Cummins sells a cleaning kit to clean the slip rings and people don't do it and it kills the voltage regulator from to much resistance

Jim Blackwood · August 28, 2018, 09:28:11 AM

Well here's a question someone should be able to answer for me, how do I tell which "Spec" this unit is? Not A. B-E maybe? F maybe? (Note, P/N is at the top of the 1st post) It is beginning to make a difference since I'm looking at the wiring diagrams.

Anyway, I've managed to identify a possibly broken wire as wire #10 on J4, the VR1 connector. Looks like it was cut, right at the end of the insulation. I initially thought maybe that was the oil level switch wire but since the connector had 12 pins instead of 15 I dug deeper.

Would that cause the no-run symptom?

Oh, and thanks for the suggestion to get a diesel genset, but this is Dave's rig. I think I may have mentioned in another thread that he ended up buying a S$S and it runs on gasoline so the diesel wouldn't be much help here. Keeping that in mind for the future though.

Time to go fix that wire it looks like.

Jim

Jim Blackwood · August 28, 2018, 10:52:51 AM

As those of you in the know will have guessed, repairing that wire did the trick. I cut the corner off the jack to expose the pin, soldered a scrap of wire to it, then spliced that back to the original wire with a lineman's splice, solder and heat shrink. None of my tools would work to release the pin from the body. So the unit started right up, and soon evened out to a steady speed, powering an incandescent bulb, one of the very few of this endangered species still remaining in captivity. But...

Not done yet. the lower third of the stainless exhaust bellows/coupler grew to a cherry red. Then on shutdown it would not restart without manual application of the choke, nor would it continue to run without it. Clearly running lean which may have been the root of the above sequence of improbable mishaps including of course, the broken wire. Should restart OK once cool again.

So...
Luvrbus you mentioned removing the altitude adjustment knob. Could you elaborate on this please? Would that make it possible to enrichen the mixture beyond the "0" setting? We are at about 500' here. (Florence, KY) I did not take the time to analyze how that metering circuit works. Can it be done without removing the bowl again? Could be the 10% ethanol fuel screwed up the calibration.

As for the tongue-in-cheek suggestion of setting up as a Onan repairman... good call but then how many would need that around Cincinnati? Not so many I'd guess.

Jim

Jim Blackwood · August 29, 2018, 09:23:19 AM

OMOA or so it seems... no problem, I'm used to it.

Bought a new HF thermo-pistol today since the old one quit. Probably 'cause it was HF. Popped the knob off the altitude adjustment knob, hey, that was easy, and opened it up a couple turns. Started up the genset and adjusted for lowest temp on the exhaust which turned out to be just under 900 F. Went richer until it started to blubber, didn't really drop the temp much at all so cranked it back in until it smoothed out. Seems about right.

Killed the motor and right away attempted restart, that didn't work. So maybe there's a timer in the controller or something. I'll let it sit a little while and try it again. I know it'll start just fine once completely cooled down but I'll see what 1/2hr does for it.

Jim

eagle19952 · August 30, 2018, 07:44:18 PM

Never met him, does he have any sisters ?

luvrbus · August 30, 2018, 08:13:32 PM

EGT's are off it seems if your H/F gun is correct , I think the timing need to be advanced it is to far retarded

Jim Blackwood · August 31, 2018, 06:33:27 AM

I richened up the mixture, I think it'll be fine. The timing is not adjustable so that's the best I can do. That's a couple hundred degrees under the melting point for aluminum so I think it'll be fine, I doubt the cylinder head gets that hot. (The stainless bellows is very thin)

Today I need to adjust the automatic choke. It starts fine when cold but won't start after it's warmed up any. Just blubbers and dies, so too much choke. After I back that off a bit it should be fine.

Still haven't got it to kick on the A/C though. Powers the fan just fine. I'm not sure what's up with that.

Not sure if you'd like his sister if she's as high maintenance and contrary as he is.

Jim