New Onan STILL not right

Carl Stouffer

Carl Stouffer

Well-known member
Jan 15, 2009
4,695
383
83
Tucson, Arizona 85718
From the old Thread (which has been split three times): "I think I'm getting to the bottom of this...finally."

The newest problem seems to be with the Onan Magna Arc electronic ignition. Symptoms are as follows:

After a successful test run under load for over an hour with a replacement fuel pump. it would not restart after I shut it down.

After checking the fuel pump function, I checked for spark and found no spark.

I hooked up the timing light and started adjusting the ignition module until I had a flash or two on the timing light.

I got lucky and got the adjustment correct and she fired right up.

After resetting the timing and adjusting the carb a little, I put a load (both Duo-Therm AC units)on it and it ran great.

After running it for an hour, I shut it down and it would not restart due to lack of spark again.

This whole scenario repeated it's self a few more times before I finally gave up (for now)

Is anyone here familiar with the Onan electronic ignition who could explain this behavior?

I hate to give up on a reasonably new ignition system, but if this is a problematic system, I'll give up on it and go with the Pertronix system.

--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Onan points are triggered by a push rod that rides on the cam which pushes the rod up to open the points. The rod may be binding in it's guide hole.
This method of opening the points is a weak spot in an otherwise simple, reliable engine. Timing will wander based on the push.
The Onan electronic system does not change this method of triggering the firing of the ignition system. This is the big advantage of the Pertronix
modification. When I had an Onan, I built an electronic ignition system that duplicated the expensive Onan method. It did improve the spark, but did
nothing for the wandering timing.
Jim Miller (Mr. Onan) may have a solution. I defer to him.
Tom, MS II
--
1975 GMC Avion
KA4CSG
 
> After running it for an hour, I shut it down and it would not restart due to lack of spark again. This whole scenario repeated it's self a few more times before I finally gave up (for now) Is anyone here familiar with the Onan electronic ignition who could explain this behavior?

Hi Carl,

I haven’t worked directly with the Magna-arc product but from an image search it appears to be some sort of points/“pertronix" lashup where the contact points are replaced by a points-like rocker arm with a magnet or pole piece mounted on it that moves in front of a pertronix-like pickup.

There may be an electronic failure in the pickup device that is triggered by heat; when the unit is running the cooling air is sufficient to prevent the failure from occurring - but when the unit is run for a while and then shut down the heat coming up from the engine block activates the failure. As a basic test you can use freeze spray (or canned air with the can turned upside down) to give the pickup unit a chill - and then attempt to re-start it. If it restarts then you may have found your problem.

Additional searching shows that the magna-arc product is discontinued but may be available from Cummins/Onan dealers like JimK as a NOS part or perhaps from ebay or wherever. I would imagine whoever installed the magna-arc discarded the original breaker points so you can’t really go back to them as a quick test unfortunately. There is always the option of the Pertronix pickup mounted in the flywheel housing but that takes a little more work to install.

Jim Miller N8ECI
1977 Eleganza
1977 Royale
Hamilton, OH
 
> When I had an Onan, I built an electronic ignition system that duplicated the expensive Onan method. It did improve the spark, but did nothing for the wandering timing.


Hi Tom,

As you have seen the cam-following pushrod method just doesn’t give enough resolution to get precise and repeatable timing regardless of whether the pushrod is triggering contact points or if it is activating some sort of electronic or VR pickup - however for the RV generator application super-precise timing doesn’t really matter IMO as long as one hasn't advanced the timing by some excessive amount that is just on the edge of causing detonation.

I think *any* electronic pickup is superior to breaker points/condenser from the standpoint of reliability. Points are notorious for pitting, getting dirty or becoming wet from condensation inside the points enclosure. Condensers go bad - which causes more pitting of the points - OR they go shorted which results in no spark at all.

The pertronix mounted in the flywheel enclosure gives an all-electronic solution that provides repeatable and reliable timing.

There’s also the solution of changing from a Kettering-type inductive ignition to a CDI type ignition and re-purposing the breaker points as the source of the timing signal to a CDI box. This approach gives a super hot spark (or multiple sparks!) and also eliminates the pitting and burning of the points because they are only providing a logic-level trigger to the CDI box. Timing will still be somewhat imprecise due to the limited resolution of the pushrod system but as I mentioned it doesn’t really matter in our application.

Just my $0.02!

—Jim


Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
Jim,

Your appraisal of the Onan electronic ignition is correct. 6-8 years ago
when I was considering making up a kit for the Pertronix upgrade, I talked
to Pertronix. They confirmed that the Onan system was, indeed, made by
them at Onan's request.

And interesting point from those discussions with Pertronix engineers:
They were concerned that with our intended application the duty cycle
would be excessive for their switching module. I never understood that
concern and the considerable empirical data the GMC community has
accumulated certainly disproves it.

IMHO, the flywheel-triggered Pertronix mod is the only sensible way to
ignite an Onan.

Ken H.

> ​...
>
​
> I haven’t worked directly with the Magna-arc product but from an image
> search it appears to be some sort of points/“pertronix" lashup where the
> contact points are replaced by a points-like rocker arm with a magnet or
> pole piece mounted on it that moves in front of a pertronix-like pickup.
> ​...
>
 
Yes, Jim's description of the workings of the Onan Magna Arc system is spot on. The pick-up unit even looks like a Pertronix unit. I guIt certainly
seems like the most logical solution to the problem. I can try cooling the pick-up unit, but all the symptoms point to a heat related failure.

Thanks everyone.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
> Onan points are triggered by a push rod that rides on the cam which pushes the rod up to open the points. The rod may be binding in it's guide
> hole. This method of opening the points is a weak spot in an otherwise simple, reliable engine. Timing will wander based on the push.
> The Onan electronic system does not change this method of triggering the firing of the ignition system. This is the big advantage of the Pertronix
> modification. When I had an Onan, I built an electronic ignition system that duplicated the expensive Onan method. It did improve the spark, but did
> nothing for the wandering timing.
> Jim Miller (Mr. Onan) may have a solution. I defer to him.
> Tom, MS II

I just happen to know what Jim Miller's solution is....
Pertronix on the flywheel.
I know he looked at a number of things and had even done a number of flywheel versions, but you will have to ask him what he thinks works best. He is
likely to have data and not just opinions too.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
> And interesting point from those discussions with Pertronix engineers: They were concerned that with our intended application the duty cycle would be excessive for their switching module. I never understood that concern and the considerable empirical data the GMC community has accumulated certainly disproves it.

Hi Ken,
Thank you for sharing that information - it is very interesting. Like you, I do not understand their concern; the Pertronix was designed to replace breaker points in distributor systems - and in a distributor on a multi-cylinder engine it would be triggering far more often than it is doing in our Onan application.
—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
Jim,

The only way I can rationalize the Pertronix concern is that the Onan, with
only one trigger per crank revolution leaves the switch ON more than a
multi-triggerr does. That would also explain why they suggested I use
their unit ffor the VW rather than the 1181 for an 8-cylinder. As it
turned out, the VW unit was less suited physically to the Onan. i've never
heard of anyone having an 1181 fail.

Ken H.

>
> > And interesting point from those discussions with Pertronix engineers:
> They were concerned that with our intended application the duty cycle would
> be excessive for their switching module. I never understood that concern
> and the considerable empirical data the GMC community has accumulated
> certainly disproves it.
>
> Hi Ken,
> Thank you for sharing that information - it is very interesting. Like you,
> I do not understand their concern; the Pertronix was designed to replace
> breaker points in distributor systems - and in a distributor on a
> multi-cylinder engine it would be triggering far more often than it is
> doing in our Onan application.
> —Jim
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
If I remember correctly, the Onan supplied electronic setup still uses the points, pushed by the pushrod. Just for the hell of it, I'd check the
point gap and set it per their recommendations. You >might< have an easy heal.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
There are no points in this system. There is a 'lever' for lack of a better description, that wags back and fourth in front of the pick-up. The
lever is actuated by the same push rod as would open and close the points.

I'll have to look at it again and see if there is an adjustment that puts the lever closer to the pick-up. I don't think it is adjustable, but I will
check when I get a chance.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
OK. I'm not familiar with it, our old Onans had points and the new ones with electronic ignition had none. We didn't run any in between. Wonder, is
the lever a Hall Effect probe or a reluctor or a photo system?

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Since it was made by Pertronix, it's almost certainly a Hall effect switch.

Ken H.

On Tue, Jul 4, 2017 at 5:18 PM, Johnny Bridges via Gmclist <

> OK. I'm not familiar with it, our old Onans had points and the new ones
> with electronic ignition had none. We didn't run any in between. Wonder,
> is
> the lever a Hall Effect probe or a reluctor or a photo system?
>
 
I used a Velleman Electronic Transistor Ignition Kit # K2545. Price is about $25. Easy to assemble. Made my Onan run much better - hotter spark.
However, by using the Onan original points as a trigger, still the problem of timing wander.
Tom, MS II
--
1975 GMC Avion
KA4CSG
 
Thomas,
The only Velleman kit I can find is the K2543 kit. The K2545 does not pop up on any of the searches that I have tried. If you have a link that would be appreciated.

JR Wright

>
> I used a Velleman Electronic Transistor Ignition Kit # K2545. Price is about $25. Easy to assemble. Made my Onan run much better - hotter spark.
> However, by using the Onan original points as a trigger, still the problem of timing wander.
> Tom, MS II
> --
> 1975 GMC Avion
> KA4CSG
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
My early morning error - K2543 is correct. Thanks for catching it. I'll correct the original entry.
Tom, MS II w/Honda ev6010
--
1975 GMC Avion
KA4CSG
 
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