| [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet [message #80346] |
Mon, 12 April 2010 16:21  |
fbhtxak
Messages: 191
Registered: April 2006
Karma: 0
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Senior Member |
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Thanks, Roy -
I did that for both the "old' capacitor and the "new" one.
Both behaved the same way. I then concluded that the
capacitance (in micro-farads) of the "new" one must have
degraded over time or was faulty at time of manufacture.
Another thing I found puzzling was use of a cheap capacitor
from a local electronics shop of the same mf rating as the
Onan capacitor. I cobbled together a means of mounting the
capacitor in place of the Onan capacitor. The engine would
not carry the load with that capacitor. 'Must not be
remembering something important about the characteristics of
capacitors ('guess I could remedy that by digging into some
of my old engineering textbooks!). I used the "generic"
capacitor to see if I could come up with an alternative to
buying an off-the-shelf Onan capacitor.
Fred Hudspeth
'78 Royale - Tyler, TX
'82 Airstream Excella 28' Motorhome - Anchorage, Alaska
Message: 4
Date: Mon, 12 Apr 2010 13:06:14 -0500
From: roy keen <roynpaula@charter.net>
Subject: Re: [GMCnet] Onan runs like Sheet: Episode II, the
Onan still
runs like sheet
To: gmclist@temp.gmcnet.org
Message-ID: <139bb.4bc36116@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"
Fred
You can get a pretty good idea if a capacitor is bad or
good by using a multi meter like a Simpson 260 (old needle
type). Put it on the high ohms scale and connect to both
sides of the capacitor . You will watch the pointer go up to
inf. as the capacitor charges then with the leads still
connected switch the meter from + to - and the meter will go
to 0 before starting to charge again , This won't tell you
the micro farads but it will tell you if it is open or
shorted.
Roy
Message: 8
Date: Mon, 12 Apr 2010 12:28:09 -0500
From: "Fred Hudspeth" <fbhtxak@sbcglobal.net>
Subject: [GMCnet] Onan runs like Sheet: Episode II, the
Onan still
runs like sheet
To: <gmclist@temp.gmcnet.org>
Message-ID: <B2633785E83F49489E1C337B8B187932@FBHVOSTRO1520>
Content-Type: text/plain; charset="us-ascii"
Shan,
If you still have the OEM breaker point ignition system, I
recommend you try a replacement ignition capacitor. A few
years ago, I had problems similar to those you describe with
the Onan in my AirstreamMh/Alaska. I concluded that fuel
delivery was OK as, without a load on the generator, the
engine operation was normal (although starting was sometimes
difficult).
I had changed the points/condenser only about 5 hours
earlier. The spark plugs looked normal. After clearing fuel
delivery, ignition points/capacitor and spark plugs as
causes, I borrowed and installed a known-good replacement
coil. 'Had no effect. Since the genset operated normally
before I changed the ignition points/capacitor, I decided to
reinstall the capacitor I removed 5 hours earlier. End of
problem!!
Why did the new capacitor not work? 'Discussed this with an
Onan engineer who is member of our local GMC Classics group.
He said this is a relatively common problem with "new" Onan
capacitors. They, however, are really NOS (new old stock)
and are prone to deteriorate with time. When there apparent
ignition problems after ignition point/capacitor change-out,
he recommended exchanging the capacitor for another one (or
install one removed when the genset was operating normally).
I did the latter as I was 100 road miles from a Cummins/Onan
dealer.
I do not know a way to conclusively check a new capacitor to
be sure it will work.
Fred Hudspeth
'78 Royale - Tyler, TX
'82 Airstream Excella 28' Motorhome - Anchorage, Alaska
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet [message #80350 is a reply to message #80346] |
Mon, 12 April 2010 17:07  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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If you believe that the problem is the capacitor across the points, convert to an electronic ignition that eliminates the need for the cap. The caps' purpose is to keep the points from burning out. Vellerman makes a $25 electronic ignition module that will do the job. However, it does not control the point at which the points case the spark plug to fire. You would still be using the cam action that is a bit sloppy in the Onan design.
On my Onan, it will fire a very rich mixture (carb problems) that would put out the spark on a conventional ignition system.
http://www.vellemanusa.com/us/enu/product/view/?id=350487
Tom Phipps,
75 GMC w/Onan
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet [message #80431 is a reply to message #80418] |
Tue, 13 April 2010 03:37 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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problem is, it retains the points with the push rod, which is the
problem......
these replace the points
http://gmcmotorhome.info/generator.html#pentronic
but then KenH gave the Onan away , anyway, (may want it back;>),
I think we should rename the GMCs, " do it because you can ;>)
gene
On Mon, Apr 12, 2010 at 9:04 PM, Shan Rose <defconfx@gmail.com> wrote:
>
>
> um how do you hook that up to an onan?
> _______________________________________________
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--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet [message #80460 is a reply to message #80434] |
Tue, 13 April 2010 11:01 |
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I'll definately look into that, but first I need to solve the initial running issues before any upgrades. since the unit ran fine and just all of a sudden started acting up, that points to some kind of component failure. the problem is finding which component failed...
| Ken Burton wrote on Tue, 13 April 2010 04:16 |
Here is the solution that you want:
http://www.gmcmhphotos.com/photos/showgallery.php?cat=3608
No points and no mechanics. With the points still used the timing bounces all over the place. With the Pertronix unit the timing is rock solid and there are no mechanics to wear or adjust. You can also adjust the timing for more advance if desired.
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73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet [message #80463 is a reply to message #80460] |
Tue, 13 April 2010 11:19 |
George Zhookoff
Messages: 398
Registered: December 2004
Location: Snellville, GA
Karma: 6
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Senior Member |
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Shan,
How did the heads look before you decarbonized them? Mine were mildly
bad.
George Zhookoff
78 EL II
Atlanta
Subject: Re: [GMCnet] Onan runs like Sheet: Episode II,the Onan still
runs like sheet
I'll definately look into that, but first I need to solve the initial
running issues before any upgrades. since the unit ran fine and just all
of a sudden started acting up, that points to some kind of component
failure. the problem is finding which component failed...
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