Home » Public Forums » GMCnet » [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet
| [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:
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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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