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Re: [GMCnet] Bringing Onan back to life due to impending hurricane [message #185477 is a reply to message #185472] Sun, 23 September 2012 11:07 Go to previous messageGo to previous message
James Hupy is currently offline  James Hupy   United States
Messages: 6806
Registered: May 2010
Karma:
Senior Member
Robin, the control board controls things like low oil level, which would
prevent the engine from running in the event of the engine being low on
oil. This is perhaps the one single biggest cause of no spark that can be
traced to the control board. There is a trick to jumper that part of the
control circuit. I believe terminal 5 and 9 can be jumpered to see if that
is the cause of your no spark. If you jumper those connectors and run the
engine with low oil level, you will damage the engine. Not good in the long
term, but for a test it is ok. Another function of the control board is to
open the fuel system solenoid valve when you attempt to start the
generator. If that function fails, no fuel will flow, and the engine will
not start. A third function of the control board is to apply the electric
choke when starting a cold engine. When the engine is warmed up, the
exhaust manifold heat warms up a thermostatic coil spring that holds the
choke in the open position when starting attempts are made to prevent
overchoking. Both the fuel system solenoid valve and the electric choke can
be jumpered with a 12 volt positive wire to test them, independently of the
control board. If they both prove functional, then this tells you that the
control board has partially failed, and would either need to be repaired or
replaced. I know that replacement control boards are available, both
cummins/onan (think $$$$$$ here) or the dinosaur boards that the GMC
vendors carry. Be advised, if a dinosaur board is fitted to your Onan and
you take it to Cummins/onan for service, they likely will tell you that
they will not work on a Genset that has a non standard control board. If
this does not resolve your no spark situation, it is likely to be the
ignition points. They need to be bright shiney not pitted clean. You can
use your wife's emery board that she uses for her fingernails, followed by
some clean card stock like a business card to absorb any oil or grease that
might be there. That should be enough to get some spark.
Jim Hupy
Salem, OR
78 GMC Royale 403

On Sun, Sep 23, 2012 at 11:30 AM, Robin Hood <loxley@gmail.com> wrote:

> Ok, so then the wires are *designed* to work like that then? That is,
> a sharp needle like projection pokes into the collection of wires at
> the center of the spark plug lead. If that's the case, then the wires
> are probably good.
>
> If i'm not seeing spark at either the points or at the end of the plug
> wires, does that mean the control board is the likely culprit? Or more
> likely the various wires. I will take contact wire to the control
> board and check the connections on each individual wire.
>
> I am THIS CLOSE to just saying screw it and taking it to the Cummins
> dealership and getting them to mess with it.
>
> I wonder how much they'll charge, and how far that would get me
> towards a new control board, new wiring harness, and new ignition
> system. I can easily seem them just wanting to replace everything till
> they got it working. Hell, even *I* could do that, I think.
>
> Argh. How frustrating.
>
>
>
> On Sat, Sep 22, 2012 at 5:20 PM, James Hupy <jamesh1296@gmail.com> wrote:
> > Robin, if you look into the top of the coil where the secondary lead
> goes,
> > you will see a sharp needle-like projection that goes into the center of
> > the lead. Onan used real wire back when these units were made. No sir,
> none
> > of that graphite impregnated nylon strand crap for them. RFI was not even
> > in the picture then. They first introduced resistor spark plugs for RFI
> > problems, and promptly cut plug service life in half, then they
> introduced
> > resistor wires, and ignition related service problems went through the
> > roof. They went away from flywheel magnetos because they didn't produce
> > enough voltage to overcome resistor crap. Now we have battery coil
> ignition
> > with contact breaker points. Not much better. Put on a pertronix solid
> > state ignition module and end the problems. JWIWD.
> > Jim Hupy
> > Salem, Or
> > 78 GMC ROYALE 403
> > On Sep 22, 2012 2:32 PM, "John Wright" <powerjon@chartermi.net> wrote:
> >
> >> Robin of the Hood,
> >> The picture was very small and hard to see.
> >>
> >> Why don't you joint the rest of us on the GMC Photo Site. Doesn't
> >> cost anything and it is where we store the GMC photo information.
> >> http://www.gmcmhphotos.com/
> >> Go to the bottom of the page and sign up for an account.
> >>
> >> JR Wright
> >> 78 Buskirk Stretch
> >> Michigan
> >>
> >>
> >>
> >> >
> >>
> http://m164.photobucket.com/albumview/albums/goodluckfox/1348348389_zps9654ea85.jpg.html?o=0&newest=1
> >> >
> >> > Is that what the spark plug wire is supposed to look like where it
> >> > plugs
> >> > into the coil? Because it looks like there's just a few strands of
> >> > wire
> >> > that don't connect to nothin.
> >> >
> >> > Tester says no spark at the plugs.
> >> >
> >> >
> >> > --
> >> > Robin Hood
> >> > Jackson, MS
> >> _______________________________________________
> >> GMCnet mailing list
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> >>
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>
>
> --
> Robin Hood
> Jackson, MS
> 2003 Buick Lesabre
> 1968 Pontiac Catalina
> 1978 GMC Royale motorhome
> 1977 GMC Palm Beach motorhome
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