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| Onan ignition questions [message #322584] |
Wed, 23 August 2017 22:22  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Ok, I have been all afternoon and early evening trying to get an Onan running.
I initially had a no spark or intermittent spark problem.
This is a wasted spark (plugs in series) system.
I initially found that the secondary coil was open (infinity). I already had an order coming from Jim K. so I had him (actually Nick) add a new Onan coil to the order. While I was waiting for it to arrive, I called Blaine and asked him to meter the secondary of a used Onan coil that he had. He read 14.5K ohms.
When the new coil arrived from Jim K. I metered it and it read 40.5 K ohms. That confused me but then I thought with my bad hearing that I mis-understood 14.5 for 40.5.
So I installed it and no spark. I metered through the plug wires and coil and still saw around 40K ohms. I cleaned and gapped the points and spark plugs. I tested the plugs on an aviation plug tester. I watched the points open and close with a test light. I checked the positive side of the coil for consistent +12 volts.
Finally I went to another hangar and took a used wasted spark coil off of an Onan engine that was mounted on a John Deer. It read the same 40.5K ohms across the secondary and still no spark. I called Blaine back and he read his again. 14.5K ohms
Tonight I got home and dug out and Onan maintenance manual. It says that the secondary should should read 14K ohms.
So now I do not understand what the differences are between our NH Onans and a these two 40.5 coils I used. I also do not understand how Jim could be selling 40K genuine Onan coils and not had previous complaints. I have not talked to Jim K yet to see if there is more than one Onan coil part number. I'll probably call him tomorrow.
At this point I think I'll probably hop in the airplane tomorrow and go get the used one that Blaine has.
One thing I have not done yet is to disconnect the condenser / capacitor across the points. There is a possibility that the condenser / capacitor is leaking.
THIS IS NOT a complaint in any way against Jim K. or Applied GMC.
I am just looking for ideas. I'm open to any thoughts.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan ignition questions [message #322585 is a reply to message #322584] |
Wed, 23 August 2017 22:48  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Ken,
I just got in the office.
I'll grab another new coil and take a OHM reading and get back.
Sice were also an ONAN dealer, we could have had one in the wrong bin.
On Wed, Aug 23, 2017 at 8:22 PM, Ken Burton wrote:
> Ok, I have been all afternoon and early evening trying to get an Onan
> running.
>
> I initially had a no spark or intermittent spark problem.
>
> This is a wasted spark (plugs in series) system.
>
> I initially found that the secondary coil was open (infinity). I already
> had an order coming from Jim K. so I had him (actually Nick) add a new Onan
> coil to the order. While I was waiting for it to arrive, I called Blaine
> and asked him to meter the secondary of a used Onan coil that he had. He
> read 14.5K ohms.
>
> When the new coil arrived from Jim K. I metered it and it read 40.5 K
> ohms. That confused me but then I thought with my bad hearing that I
> mis-understood 14.5 for 40.5.
>
> So I installed it and no spark. I metered through the plug wires and coil
> and still saw around 40K ohms. I cleaned and gapped the points and spark
> plugs. I tested the plugs on an aviation plug tester. I watched the
> points open and close with a test light. I checked the positive side of the
> coil for consistent +12 volts.
>
> Finally I went to another hangar and took a used wasted spark coil off of
> an Onan engine that was mounted on a John Deer. It read the same 40.5K
> ohms across the secondary and still no spark. I called Blaine back and he
> read his again. 14.5K ohms
>
> Tonight I got home and dug out and Onan maintenance manual. It says that
> the secondary should should read 14K ohms.
>
> So now I do not understand what the differences are between our NH Onans
> and a these two 40.5 coils I used. I also do not understand how Jim could
> be
> selling 40K genuine Onan coils and not had previous complaints. I have
> not talked to Jim K yet to see if there is more than one Onan coil part
> number. I'll probably call him tomorrow.
>
> At this point I think I'll probably hop in the airplane tomorrow and go
> get the used one that Blaine has.
>
> One thing I have not done yet is to disconnect the condenser / capacitor
> across the points. There is a possibility that the condenser / capacitor is
> leaking.
>
> THIS IS NOT a complaint in any way against Jim K. or Applied GMC.
>
> I am just looking for ideas. I'm open to any thoughts.
>
> Ken B.
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> 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@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Onan ignition questions [message #322586 is a reply to message #322585] |
Wed, 23 August 2017 23:21 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Ok Jim, You can call here if you want. It was not until a hour ago or so ago when I read the manual that I am thinking that I might have the wrong coil. Unfortunately the box is at the airport and I'm at home now. So I can not tell you the exact part number that I received. I was thinking about calling you tomorrow but I am up right now if you ant to call me.
Ken
Thanks Jim
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan ignition questions [message #322589 is a reply to message #322584] |
Thu, 24 August 2017 01:02 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Ken,
Just buy one of these:
http://www.jpcycles.com/product/3000140
They come with two plug wires too boot!
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of Ken Burton
Sent: Thursday, August 24, 2017 1:22 PM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Onan ignition questions
Ok, I have been all afternoon and early evening trying to get an Onan running.
I initially had a no spark or intermittent spark problem.
This is a wasted spark (plugs in series) system.
I initially found that the secondary coil was open (infinity). I already had an order coming from Jim K. so I had him (actually
Nick) add a new Onan coil to the order. While I was waiting for it to arrive, I called Blaine and asked him to meter the secondary
of a used Onan coil that he had. He read 14.5K ohms.
When the new coil arrived from Jim K. I metered it and it read 40.5 K ohms. That confused me but then I thought with my bad hearing
that I mis-understood 14.5 for 40.5.
So I installed it and no spark. I metered through the plug wires and coil and still saw around 40K ohms. I cleaned and gapped the
points and spark plugs. I tested the plugs on an aviation plug tester. I watched the points open and close with a test light. I
checked the positive side of the coil for consistent +12 volts.
Finally I went to another hangar and took a used wasted spark coil off of an Onan engine that was mounted on a John Deer. It read
the same 40.5K ohms across the secondary and still no spark. I called Blaine back and he read his again. 14.5K ohms
Tonight I got home and dug out and Onan maintenance manual. It says that the secondary should should read 14K ohms.
So now I do not understand what the differences are between our NH Onans and a these two 40.5 coils I used. I also do not
understand how Jim could be selling 40K genuine Onan coils and not had previous complaints. I have not talked to Jim K yet to see
if there is more than one Onan coil part number. I'll probably call him tomorrow.
At this point I think I'll probably hop in the airplane tomorrow and go get the used one that Blaine has.
One thing I have not done yet is to disconnect the condenser / capacitor across the points. There is a possibility that the
condenser / capacitor is
leaking.
THIS IS NOT a complaint in any way against Jim K. or Applied GMC.
I am just looking for ideas. I'm open to any thoughts.
Ken B.
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Onan ignition questions [message #322591 is a reply to message #322584] |
Thu, 24 August 2017 06:21 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Senior Member |
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> On Aug 23, 2017, at 11:22 PM, Ken Burton wrote:
>
> I watched the points open and close with a test light.
> One thing I have not done yet is to disconnect the condenser / capacitor across the points.
Hi Ken,
Capacitors are notorious failure items — always always consider them early on in the ignition troubleshooting process. In addition to its role of quenching the arc across the points when they open, the condenser forms half of an LC network between the coil primary and itself. As the points open and the magnetic field in the coil collapses it sends some energy back into the primary and this LC network on the primary side serves to temporarily store that energy and “push” it back into the coil where it contributes to the secondary’s discharge voltage.
Also consider that RFI filter that attaches to the coil - if your unit still has it; I’ve seen these act up as well.
I’ve used JimK’s coils as well as some dual-tower Denso’s that I’ve scavenged off of modern small engines - they all work fine - and several of the ones I’ve scavenged have had 30-40kOhm secondaries. I would argue that the inductance characteristics of the coil’s primary and secondary is of more import than the resistance.
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 ignition questions [message #322600 is a reply to message #322584] |
Thu, 24 August 2017 08:48 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Guessing--the new ones have more secondary turns to give updated output? I with Jim on the caps. Hard to test and prove good but will bugger the system if bad.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Onan ignition questions [message #322602 is a reply to message #322591] |
Thu, 24 August 2017 08:52 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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|
Thanks Jim.
I removed the RFI capacitor yesterday. I just did not mention it in my posting.
It looks like the first thing I need to do today is go after to go after the capacitor across the points. Jim K. called me just before midnight. He measured another coil that he had is stock and it came up at 38K. He also told me that he has sold more than a few of these and never had anyone say that they did not work. So I guess I need to put that resistance difference aside and look elsewhere.
Both you and Jim K. have pretty much convinced me this new coil is not the problem.
If I do not get anywhere with the capacitor, there is another used coil on a Kohler engine that I'll look at "borrowing" to try. After that I'll probably fly down to Blaine's and get the used Onan one that he has.
This bug is really exasperating.
Thanks again for the help.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan ignition questions [message #322617 is a reply to message #322585] |
Thu, 24 August 2017 16:26 |
fbhtxak
Messages: 191
Registered: April 2006
Karma: 0
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Senior Member |
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Ken,
I have had similar experience to that you described with two 6.5KW Onan gen
sets - the one in my GMCMh and the one in my Alaska Airstream Mh . After
running all of the "traps" you did, I found the ignition capacitors to be
the culprit. After replacing the capacitors, with all other aspects of the
ignition system on-spec, the gen sets performed normally. 'Caution - some
capacitors, especially NOS, may be defective "right out of the box". I had
that experience with OEM capacitors from a supplier near my Texas home. If
available, 'best to test, using a known good capacitor.
'Hope this helps...
Fred
Fred Hudspeth
1978 Royale (TZE 368V101335) - Tyler, TX
1982 Airstream Excella (motorhome) - Cooper Landing, Alaska
Message: 3
Date: Thu, 24 Aug 2017 07:52:50 -0600
From: Ken Burton
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Onan ignition questions
Message-ID:
Content-Type: text/plain; charset="utf-8"
Thanks Jim.
I removed the RFI capacitor yesterday. I just did not mention it in my
posting.
It looks like the first thing I need to do today is go after to go after the
capacitor across the points. Jim K. called me just before midnight. He
measured another coil that he had is stock and it came up at 38K. He also
told me that he has sold more than a few of these and never had anyone say
that they did not work. So I guess I need to put that resistance difference
aside and look elsewhere.
Both you and Jim K. have pretty much convinced me this new coil is not the
problem.
If I do not get anywhere with the capacitor, there is another used coil on a
Kohler engine that I'll look at "borrowing" to try. After that I'll
probably fly down to Blaine's and get the used Onan one that he has.
This bug is really exasperating.
Thanks again for the help.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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GMCnet mailing list
Unsubscribe or Change List Options:
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| Re: [GMCnet] Onan ignition questions [message #322619 is a reply to message #322585] |
Thu, 24 August 2017 16:44 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I have found that capacitors for Onan engines come at least two ways.
One is a thin metal tube, with a pack of foil and insulation wound into a
minature toilet paper roll. Then, a black fibre washer follows that with a
insulated conductor emanating from the center of the disc. No sealant
visible. The end of the can is then rolled over the edge. I have found this
type to fail often.
The second type, still has a metal outer shell, but has what looks to be an
epoxy sealant on the open end with a conductor coming through the sealant.
O have rarely known those to fail. I expect that the latter type are
military spec. I always try to find them if available. Keep the known good
ones for a spare, or, install an electronic ignition. (Better)
Jim Hupy
Salem, Or.
On Aug 24, 2017 2:27 PM, "Fred Hudspeth" wrote:
Ken,
I have had similar experience to that you described with two 6.5KW Onan gen
sets - the one in my GMCMh and the one in my Alaska Airstream Mh . After
running all of the "traps" you did, I found the ignition capacitors to be
the culprit. After replacing the capacitors, with all other aspects of the
ignition system on-spec, the gen sets performed normally. 'Caution - some
capacitors, especially NOS, may be defective "right out of the box". I had
that experience with OEM capacitors from a supplier near my Texas home. If
available, 'best to test, using a known good capacitor.
'Hope this helps...
Fred
Fred Hudspeth
1978 Royale (TZE 368V101335) - Tyler, TX
1982 Airstream Excella (motorhome) - Cooper Landing, Alaska
Message: 3
Date: Thu, 24 Aug 2017 07:52:50 -0600
From: Ken Burton
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Onan ignition questions
Message-ID:
Content-Type: text/plain; charset="utf-8"
Thanks Jim.
I removed the RFI capacitor yesterday. I just did not mention it in my
posting.
It looks like the first thing I need to do today is go after to go after the
capacitor across the points. Jim K. called me just before midnight. He
measured another coil that he had is stock and it came up at 38K. He also
told me that he has sold more than a few of these and never had anyone say
that they did not work. So I guess I need to put that resistance difference
aside and look elsewhere.
Both you and Jim K. have pretty much convinced me this new coil is not the
problem.
If I do not get anywhere with the capacitor, there is another used coil on a
Kohler engine that I'll look at "borrowing" to try. After that I'll
probably fly down to Blaine's and get the used Onan one that he has.
This bug is really exasperating.
Thanks again for the help.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
_______________________________________________
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Unsubscribe or Change List Options:
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| Re: [GMCnet] Onan ignition questions [message #322627 is a reply to message #322617] |
Fri, 25 August 2017 02:35 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Jim and Fred, we pulled the capacitor today and still no fire at all. I then reinstalled the original bad coil which has an intermittent secondary. It fired and ran intermittently.
We reinstalled the two new coils and nothing. Finally the guy working with me said. lets do this dynamically. So while I held the start button he cranked on the adjustment. After a couple of turns it fired sporadically. Eventually we got it to run and fine tuned the points setting until it ran smoothly. We have effectively increased the dwell time. It runs fine now and the points are much closer than the .020 spec. We reinstalled the capacitor and it still runs fine.
Evidently these higher impedance coils take a longer dwell. I did not measure the final clearance and look at the timing. The points cover is back on and we moved on to other problems ike no start / run without jumpering Pin 9 to +12 volts and no power out of the generator. Found a bad full wave bridge and replaced it. We still have no 120V power. We will continue on this tomorrow.
Thanks for the help everybody.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan ignition questions [message #322630 is a reply to message #322627] |
Fri, 25 August 2017 08:39 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Ken,
We have the luxury of having all the parts here to use on these Onan and
sometimes when all things fail, we try new parts. Believe it or not, the
parts cost lot less than labor and it works better.
On Fri, Aug 25, 2017 at 12:35 AM, Ken Burton wrote:
> Jim and Fred, we pulled the capacitor today and still no fire at all. I
> then reinstalled the original bad coil which has an intermittent secondary.
> It fired and ran intermittently.
>
> We reinstalled the two new coils and nothing. Finally the guy working
> with me said. lets do this dynamically. So while I held the start button
> he
> cranked on the adjustment. After a couple of turns it fired
> sporadically. Eventually we got it to run and fine tuned the points
> setting until it ran
> smoothly. We have effectively increased the dwell time. It runs fine now
> and the points are much closer than the .020 spec. We reinstalled the
> capacitor and it still runs fine.
>
> Evidently these higher impedance coils take a longer dwell. I did not
> measure the final clearance and look at the timing. The points cover is
> back
> on and we moved on to other problems ike no start / run without jumpering
> Pin 9 to +12 volts and no power out of the generator. Found a bad full wave
> bridge and replaced it. We still have no 120V power. We will continue
> on this tomorrow.
>
> Thanks for the help everybody.
>
> Ken B.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> 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@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Onan ignition questions [message #322631 is a reply to message #322630] |
Fri, 25 August 2017 09:02 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Senior Member |
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On Aug 25, 2017, at 9:39 AM, Jim Kanomata wrote:
> We have the luxury of having all the parts here to use on these Onan and sometimes when all things fail, we try new parts. Believe it or not, the parts cost lot less than labor and it works better.
I still contend that Ken’s condenser is on its way to failure. There’s no requirement for “extra dwell” on the newer coils and the points should not have had to be adjusted far from spec in order to make the machine run. I feel that his condenser has lost capacitance over time and probably also has increased series resistance and is thus not contributing as it should to the LC circuit formed by the condenser and the coil primary.
Condensers are dirt cheap and available everywhere. I always change them out if there’s any doubt whatsoever about their characteristics.
—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 ignition questions [message #322635 is a reply to message #322631] |
Fri, 25 August 2017 11:58 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Jim is probably correct on the capacitor.
I do not have the luxury of running down the street and getting parts. The capacitor has a unique way of mounting so it runs the way it is and I'm leaving it that way.
I still have two other Onan problems to resolve and that is today's project.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan ignition questions [message #323682 is a reply to message #323679] |
Sun, 10 September 2017 00:22 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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k2gkk wrote on Sat, 09 September 2017 21:20Isn't the Onan running wasted spark where both plugs fire simultaneously even though only one cylinder is on the power stroke? Both plugs have fire in order for the motor to operate.
Mac in OKC
"The Money Pit"
YES.
The plugs are wired in series. If one is unplugged the other will not fire. In this arrangement the spark must jump across both plugs at the same time. The Onan ignition is a weak one so the plug gaps MUST be set exactly. That gap is .020". New plugs are usually set too wide and need to be re-gapped down to .020".
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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