1973 4K generator

T

Thigh19

New member
Aug 4, 2019
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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
 
http://www.gmcws.org/Tech/dsimmons/onan/onan.html

More info on generator
http://bdub.net/gmcmotorhome.info/list.html

On Mon, Oct 14, 2019 at 6:01 PM Thom High via Gmclist <

> 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
 
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
 
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
 
How hard was it to install? Is it plug and play or was there any modifications needed?
Thanx in advance
Thom High
 
> How 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
 
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
 
> 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.

More info and/or pics?
 
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?

> 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
 
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 <

> 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?
>
>
>
>
>

> > 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
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
OK, have you checked the oil level? And the low oil pressure switch?

Nelson Wright6r
Sent from my iPad

>
> 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
 
Got it running, running good and generating, but choke needs adjusting and I'm not sure how. Any help?
 
Generally the hoke comes on for a second and opens up.
there is a wire and a slide fastener so one can slide the fitting and
tighten the screw.
Choke comes on when cranking and pulls off once the engine start.

On Sat, Nov 16, 2019 at 3:26 PM Thom High via Gmclist <

> Got it running, running good and generating, but choke needs adjusting and
> I'm not sure how. Any help?
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmcrvparts.com
1-800-752-7502
 
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
 
>
> […] 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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