| 1973 4K generator [message #349287] |
Mon, 14 October 2019 19:00  |
thigh19
Messages: 92
Registered: July 2019
Location: Vancouver Wa
Karma: 1
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Been trying to figure out my Onan generator. Rebuilt carburetor, rebuilt/replaced fuel pump. Wouldn't start. Then went back to basics. Ran power jumper to coil, started up and ran good and smooth. My question is, what powers up the coil? Sure it's something simple,but searching the internet, I've found nothing. And as far as I can tell, most all the wires are the same color, or painted Onan green. Any help will be appreciated
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| Re: [GMCnet] 1973 4K generator [message #349289 is a reply to message #349287] |
Mon, 14 October 2019 19:27  |
Bruce Hart
Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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http://www.gmcws.org/Tech/dsimmons/onan/onan.html
More info on generator
http://gmcmotorhome.info/list.html#GEN
On Mon, Oct 14, 2019 at 6:01 PM Thom High via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Been trying to figure out my Onan generator. Rebuilt carburetor,
> rebuilt/replaced fuel pump. Wouldn't start. Then went back to basics. Ran
> power
> jumper to coil, started up and ran good and smooth. My question is, what
> powers up the coil? Sure it's something simple,but searching the internet,
> I've found nothing. And as far as I can tell, most all the wires are the
> same color, or painted Onan green. Any help will be appreciated
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: 1973 4K generator [message #349292 is a reply to message #349287] |
Mon, 14 October 2019 20:15 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Controlled by the Onan control board. It is on the same circuit as the fuel pump and fuel valve if you have one.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: 1973 4K generator [message #349299 is a reply to message #349287] |
Tue, 15 October 2019 08:09 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Basic theory is the small alternator under the flywheel (not the rear main 125VAC unit) produces an approximate 30V to to board. This tells the logic that the engine is running and locks out the starter while latching 12V to coil and fuel pump.
Check the wiring at the voltage regulator on top of Onan. Originally this charged the garden tractor battery on early coaches. There is a "twofer" faston connection where two wires are joined and are taped up if the garden tractor battery charge function has been bypassed. If there is no 30V to the board it will think the unit us not running. Details are in writeups.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: 1973 4K generator [message #349321 is a reply to message #349318] |
Wed, 16 October 2019 08:54 |
Justin Brady
Messages: 769
Registered: April 2015
Location: Bell Buckle, TN
Karma: 11
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thigh19 wrote on Tue, 15 October 2019 23:19How hard was it to install? Is it plug and play or was there any modifications needed?
Thanx in advance
Thom High
It's a direct replacement. Plug and play.
Just get the model number off your current board to confirm it's the correct replacement.
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455
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| Re: 1973 4K generator [message #349834 is a reply to message #349830] |
Sun, 03 November 2019 12:36 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Sir, on a 6 k the actual running of the engine is controlled by the board but the initial starting is controlled by a wire from the starter solenoid. Since you have replaced the board, maybe start the Onan using your jumper, then after it starts and clears out remove jumper and see if it stays running. If it does you can move the initial wire from small terminal on solenoid to large terminal going to starter. This works on a 6 k and am not sure it is the same solenoid configuration on 4 k but if both use same board it should be same also?
thigh19 wrote on Sun, 03 November 2019 12:58Okay, replaced the board with a flight system board and still won't start, any other ideas? Rebuilt the carb, was filthy, new fuel, pump filter, just at wits end. Don't want to take it toCummins(Onan), but running out of options
C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] 1973 4K generator [message #349835 is a reply to message #349834] |
Sun, 03 November 2019 12:43 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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As Chuck said, you should be able to get it to start w/o the board at all.
Look up Duane Simmons Onan troubleshooting chart. It’s one-two pages max
and has all you need to figure out why it will not do whatever and how to
isolate/fix the cause. Spend the time to find it and print it out/take it
with you to the generator and spend waaay less time on the diagnostic.
Sully
Bellevue wa.
On Sun, Nov 3, 2019 at 10:36 AM Charles Boyd via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Sir, on a 6 k the actual running of the engine is controlled by the board
> but the initial starting is controlled by a wire from the starter solenoid.
> Since you have replaced the board, maybe start the Onan using your jumper,
> then after it starts and clears out remove jumper and see if it stays
> running. If it does you can move the initial wire from small terminal on
> solenoid to large terminal going to starter. This works on a 6 k and am not
> sure it is the same solenoid configuration on 4 k but if both use same
> board it should be same also?
>
>
>
>
>
> thigh19 wrote on Sun, 03 November 2019 12:58
>> Okay, replaced the board with a flight system board and still won't
> start, any other ideas? Rebuilt the carb, was filthy, new fuel, pump filter,
>> just at wits end. Don't want to take it toCummins(Onan), but running out
> of options
>
>
> --
> C. Boyd
> 76 Crestmont
> East Tennessee
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] 1973 4K generator [message #349856 is a reply to message #349830] |
Mon, 04 November 2019 02:14 |
Nelson
Messages: 120
Registered: August 2014
Karma: 0
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OK, have you checked the oil level? And the low oil pressure switch?
Nelson Wright6r
Sent from my iPad
> On Nov 4, 2019, at 6:59 AM, Thom High via Gmclist wrote:
>
> Okay, replaced the board with a flight system board and still won't start, any other ideas? Rebuilt the carb, was filthy, new fuel, pump filter, just
> at wits end. Don't want to take it toCummins(Onan), but running out of options
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: 1973 4K generator [message #350160 is a reply to message #349287] |
Sat, 16 November 2019 19:14 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Choke works as follows. The choke solenoid is energized only during cranking. The solenoid output moves a bimetallic spring, which is connected to the output lever. If COLD The bimetallic spring allows full lever deflection. When HOT the bimetallic spring does not allow the solenoid to actuate the lever. It's somewhat variable at intermediate temps. Often the mechanism just needs to be freed and lubed. Another fault is poor ground of choke to manifold. Some add an aux ground wire for better ground.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] 1973 4K generator [message #350163 is a reply to message #350160] |
Sat, 16 November 2019 19:41 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Senior Member |
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> On Nov 16, 2019, at 8:14 PM, John R. Lebetski via Gmclist wrote:
>
> […] Often the mechanism just needs to be freed and lubed. Another fault is poor ground of choke to manifold. Some add an aux ground wire for better ground.
There are almost no lubes other than graphite that will survive the heat at the mounting point on the exhaust manifold without turning to sticky goo (which interferes with proper choke operation) or carbon. The OEM product had no lube and depended on clearance between the rotating shaft and the actuator body for proper operation.
The additional ground wire that John mentions is highly recommended as over 40 years of elapsed time the electrical connection between the actuator and the manifold has deteriorated considerably due to rust. If you add the ground wire then keep in mind that the temperature at the manifold and actuator is around 600F so choose your wire and wire connector appropriately.
—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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