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
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
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
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.
ok
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
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.😋
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
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
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
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
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
Never met him, does he have any sisters ? :)
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
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
Sure the timing is adjustable they retard those for propane use
I don''t see how. The magnet is in a fixed position on the flywheel. There is only one keyway. The magneto bolts into the end bell in a single fixed position. There are no further electronic controls other than shutoff. How could you possibly adjust it?
Maybe on the propane models they use a different flywheel. I think in the manual it says the timing is not adjustable, set at 25*BTDC (specifications).
Jim
I have an issue with the choke linkage, it won't let the engine start unless it is dead cold and no adjustment of the bi-metal spring helps that. Overly rich.
On the carb, the choke flapper has a tab that engages a cam on the throttle arm to hold the choke open while running. a separate arm engages the choke linkage to the bi-metal. There is a light concentric spring that nudges the choke plate towards the closed position. I'm attempting to attach 2 photos but they might be too big, we'll see.
What happens is that the choke needs to be open to start once the engine has run just a little but the spring urges it closed. Intake pulsations make it flutter around a little but it's still too much. Once the governor begins to back off the cam holds it open but for starting it is just way too rich if there is any heat in the engine at all. Cold it works just fine, in fact backing off the bi-metal makes it too lean to start.
I know these normally work correctly so what gives? Is the concentric spring supposed to move the choke tab the other way maybe?
Jim
Can of dust-off on hand....?
Dust-off for Onan's sister? Man, you are a cold one.
Anyway here's a shot showing how I think the spring is supposed to go. Seems to work anyway. One more test tomorrow to set the choke for cold start and it should be done and dusted. You should be able to see in the first photo how the spring position was different.
Jim
Does it ever end?
How do things get so weird? Now I've discovered that the bi-metal is somehow set up so that it closes the choke when the engine gets hot! ?????
That's right, I didn't make that up, and I do know how it is supposed to work. After sitting overnight the choke was open but the motor started fairly easily. After running five minutes the throttle cam was holding the choke open but once I stopped the engine it went fully closed.
I'v got to wait for it to cool down before I can get in there to disassemble and see what's up with that. Maybe the bi-metal was put in backwards.
Jim
All this gobbliegoop will continue as long as you have an Onan gasoline. I have a Powertech 10kw Diesel gen with about 1,200 hrs on it. Brushless altenator, 4 cylinder Kubota. Except for changing the coolant and oil, have done nothing else to it. Get a Diesel genset-you'll be much happier. Good Luck, TomC
I thought the choke always went back to the closed position it does on my Onan,then when starting when hot it opens when you try to start
Quote from: TomC on September 01, 2018, 09:00:55 AM
All this gobbliegoop will continue as long as you have an Onan gasoline. I have a Powertech 10kw Diesel gen with about 1,200 hrs on it. Brushless altenator, 4 cylinder Kubota. Except for changing the coolant and oil, have done nothing else to it. Get a Diesel genset-you'll be much happier. Good Luck, TomC
Tom, it's gasoline for a good reason.
Quote from: Jim Blackwood on September 01, 2018, 08:42:45 AM
Does it ever end?
After running five minutes the throttle cam was holding the choke open but once I stopped the engine it went fully closed.
I'v got to wait for it to cool down before I can get in there to disassemble and see what's up with that.
Jim
ok. ice cubes, to trick the choke ?
BTW. just kidding.
Thanks guys, all suggestions gratefully appreciated, even the funny ones. :D
As it turns out, and often the case it's a good idea to take pictures before disassembly even for apparently simple things. After going to the trouble of removing the choke bi-metal and choke stove (and yes, it can be done while leaving everything else intact including the case but it isn't exactly fun) and then testing the bi-metal with my lighter, I though to myself..."Self, don't you think maybe there could be some other cause..."
And sure enough, right there it was right on top of the carb. Now mind you it wasn't obvious which is why nobody picked up on it from the photos and pointed it out to me but that little tab that the choke rod connects to is supposed to be back BEHIND the shaft, not in front of it. It reverses the operation. And there is a strategically placed dimple in the air cleaner base that will not let it be rotated from one side to the other without loosening that plate from the carb. So, whatever side it is on when the carb is bolted up, it's stuck there.
After putting it on the back side, amazingly enough the little limiter tab on the choke tab lined up and functioned as a choke pull-off and the concentric spring now fit into the holes and appears to function as it should. Such wonderfully brilliant engineers they had at Onan to come up with alternate ways to put their parts together. It makes such a delightful puzzle.
So anyway, warmup tests are good and I think the cold test tomorrow will be as well.
And then I'm done with it. Not my genset, not my RV. Dave's problem after that. (Of course, being my oldest son he might be inclined to ask dear old dad for help and that being an excuse for a visit I might be inclined to take a look. But we'll see.)
Jim
Were those ice cubes for Onan's sister? I've heard about that trick...
What made the exhaust glow red? Retarded timing?
Lean mixture. I suspect it might have had something to do with alcohol in the gas these days but who knows? Richened it up and it worked fine.
Jim
We had a resident Onan expert and dealer in DaveG here that answered all our question about Onan, even where to buy the boards at a huge saving but Dave passed away a few years ago.
Check the mix at full load. Adjust to be ever slightly rich.
We'd been running a 6.5kw NH series 1800 rpm since 1985 without issue. Ie:after we upgraded with electronic ignition & a carb preheat kit. Fwiw.
Quote from: chessie4905 on September 01, 2018, 12:33:47 PM
Check the mix at full load. Adjust to be ever slightly rich.
Yep. Did that.
Jim
You going to re install the knob ? now you know you can adjust the carburetor 8)
Yep. Did that too.
Jim