| Re: Onan issues [message #308142 is a reply to message #307986] |
Sun, 02 October 2016 14:42   |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
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Got it going and as long as I keep the switch pushed and the carb pulled open, it will run. As soon as I let go of the carb wire it shuts and the engine chokes out. IF I keep hold of the choke so it's open and let go of the start button it goes out. Of course if I leave it jumped from 5 to 9 it continues to run. I think I can, I think I can...
-James Palmer, Traverse City, MI
1976 Eleganza
[Updated on: Sun, 02 October 2016 14:54] Report message to a moderator |
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| Re: Onan issues [message #308143 is a reply to message #308142] |
Sun, 02 October 2016 15:06 |
A Hamilto
Messages: 4508
Registered: April 2011
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Palmerdad wrote on Sun, 02 October 2016 14:42Got it going and as long as I keep the switch pushed and the carb pulled open, it will run. As soon as I let go of the carb wire it shuts and the engine chokes out. IF I keep hold of the choke so it's open and let go of the start button it goes out. I think I can, I think I can... Is the starter still spinning it when it is trying to run or has it disengaged and the Onan running under its own power and the start button just seems to be keeping the ignition energized?
If the starter is still spinning it, it might be not getting enough gas to run. If the starter is not keeping it spinning (it is getting enough gas to run), it might be that the board is not getting voltage on pin 8 so it turns off the spark, and you are overriding that with the start switch.
What happens when you jumper pin 5 to 9? That should force spark and fuel pump no matter what pin 8 sees. If it won't run then, it just about has to be a fuel problem.
Also make sure you have enough oil in it. AND make sure all the circuit breakers inside are OFF. I don't think it will start under load.
Since it gets fire at crank, the ignition system is sound. Gotta be something turning off the spark, or a fuel delivery problem. Both curable.
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| Re: Onan issues [message #308152 is a reply to message #308145] |
Sun, 02 October 2016 18:49 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
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When 5 to 9 is jumped it keeps running and I was able to run it for about 10 minutes until it started to rain and I packed it all away for the day. I've been looking at Mr. Simmons sheets and it appears that I'm getting down to it being the control board. I tried taping up the voltage regulator wires. Tried removing 1-3 and also removing the LOP #12. I didn't necessarily try all three of these at once but I don't think that is what he is advocating. None of these kept it running without the jumper. Sounds like my last question is where is the best place to buy a new control board?!?
Suspect low AC voltage (terminal 8 to 11) must be 26 to 30 VAC running
! Disable / disconnect Onan voltage regulator wiring
! Remove single wire and tape up without touching ground or other wires
! Remove double wire with adapter (keep connected) and tape up without touching ground or other wires
Suspect remote control panel or wiring faulty
! Remove wires from upper terminals 1, 2 and 3 and try running again.
Suspect faulty low oil pressure (LOP) switch or wiring failure
! Remove wire from board terminal 12 and try running again
Suspect control board faulty
! Test and / or repair board as required
-James Palmer, Traverse City, MI
1976 Eleganza
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| Re: Onan issues [message #308153 is a reply to message #308142] |
Sun, 02 October 2016 18:57 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Palmerdad wrote on Sun, 02 October 2016 14:42...if I leave it jumped from 5 to 9 it continues to run. ... The two things that will make it shut itself off are: Doesn't know it is running because it doesn't see enough voltage at pin 8 (voltage from the flywheel alternator). Or thinks the oil pressure is low (the low oil pressure switch, or something else is grounding pin 12).
When it is running, make sure you have 26 - 30 VDC on pin 8. If it does, lift pin 12 and then unjumper 5 and 9 to see if it keeps running. If it keeps running, your oil pressure switch is telling the board there isn't enough oil pressure. It might be right, OR it might need to be replaced.
If a PO has incorrectly disconnected the voltage regulator, and didn't leave the connection from the flywheel alternator to pin 8 (or corrosion on the connections), that will shut down the generator. And a bad oil pressure switch will too. And it also might actually have low oil pressure.
If you got enough voltage at pin 8 and the oil pressure switch is not stuck in short circuit mode, I suspect the board.
If you are pretty sure you do not have low oil pressure, run it with the jumper from 5 - 9. Check an inside outlet for 120V. Then try running the roof AC. If it runs the roof AC, you got a good genset and it would be worthwhile to service or replace the board.
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| Re: Onan issues [message #308156 is a reply to message #308153] |
Sun, 02 October 2016 19:36 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
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I guess I honestly hadn't thought about the possibility of it not powering into the GMC once I got it running! What goes wrong with them where they wouldn't make power?
-James Palmer, Traverse City, MI
1976 Eleganza
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| Re: [GMCnet] Onan issues [message #308160 is a reply to message #308156] |
Sun, 02 October 2016 19:47 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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On Oct 2, 2016, at 8:36 PM, James Palmer wrote:
> I guess I honestly hadn't thought about the possibility of it not powering into the GMC once I got it running! What goes wrong with them where they wouldn't make power?
In decreasing order of likelihood:
1. Loss of magnetism in the field if it has been sitting unused for a significant time (needs flashing procedure)
2. Defective bridge rectifier.
3. Damaged coil(s) in the field assembly.
4. Damaged armature (coils, slip rings, or brushes)
5. Defective excitation circuit (bad compounding reactor = no power, bad thyristor = too much voltage).
—Jim
Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: Onan issues [message #308172 is a reply to message #307986] |
Sun, 02 October 2016 23:02 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
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How does one test the bridge rectifier? Seems that these are cheap to replace if that's the issue. And as far as sitting for a long time, I would say that describes this gen pretty well. What is the "flashing procedure"?
-James Palmer, Traverse City, MI
1976 Eleganza
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| Re: [GMCnet] Onan issues [message #308176 is a reply to message #308173] |
Mon, 03 October 2016 06:38 |
Jim Miller
Messages: 501
Registered: March 2008
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On Oct 3, 2016, at 12:20 AM, A. wrote:
> They almost never need to be "flashed".
I’d beg to differ - of the dozens of units that have been through the Miller compound at our work rallies - and many more that I’ve helped people repair from afar - there were many that needed flashed. This includes some that had sat idle for only a year or two. In fact, I’ve seen more that needed flashed than needed bridge rectifiers.
In any case the original poster was asking about what *can* go wrong and thus the flashing procedure was listed for completeness.
Of course he should test it for AC output before doing anything else!
—Jim
Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: [GMCnet] Onan issues [message #308179 is a reply to message #308135] |
Mon, 03 October 2016 07:27 |
mghamms
Messages: 466
Registered: March 2016
Location: Ware, Massachusetts
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Looks to me to be time to replace that old board to save a lot of agrivation.
Dino boards are only about $135.00 and well worth it.
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
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| Re: [GMCnet] Onan issues [message #308217 is a reply to message #308191] |
Mon, 03 October 2016 20:50 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
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Got busy today and didn't have much time to work on it. I did check the electrical inside while the generator was running and I don't have any. I had it hooked up to power at a campground 2 weeks ago and everything ran so I know the problem is generator related. I'll get the voltage numbers for pin 8 tomorrow. I made an amazon order today so I included the bridge rectifier. (They're pretty cheap.) If that's not the problem at least I'll have a spare. Does anyone have "idiot proof" instructions on how to do the flashing procedure? Any Youtube videos out there?!? I assume it doesn't hurt the unit to do this if it turns out that it wasn't necessary?
-James Palmer, Traverse City, MI
1976 Eleganza
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| Re: Onan issues [message #308220 is a reply to message #307986] |
Mon, 03 October 2016 21:11 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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You have not answered these questions as far as I can see
1) is the oil level correct
2) do you have at least 1/2 tank of fuel? GM upfit coaches shut off gen at about 1/4 tank
I would get it running right and then meter on both sides of the main breaker Using a meter correctly for ACV,DCV and ohms saves throwing parts at it and lots of time.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Onan issues [message #308235 is a reply to message #308220] |
Mon, 03 October 2016 23:00 |
Palmerdad
Messages: 60
Registered: August 2016
Location: Traverse City
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Sorry, yes, I just changed the oil and filter and have triple checked the level before and after getting it running. It is right up to the full line. And I had just topped off the GMC fuel tanks before starting in on the Onan. Breaker button is pushed in. I should probably check that current is going through it though as I have heard these can go bad.
Didn't know there was a procedure for changing from shore power to generator. Is there something I'm supposed to change?
-James Palmer, Traverse City, MI
1976 Eleganza
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