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[GMCnet] Onan [message #75986]

Mon, 08 March 2010 11:29

amansfield1104

Messages: 80
Registered: August 2009

Karma: 0

Member

I have just replace the points ignition wires and plugs. I tried to adjust the carb but it did not help. The compression is 125psi on both cylinders.

It ran ok until it warmed up. Then it starts missing. I took the cover off of the points and they look fine, no missing. I am waiting for it to cool off and see if it still runs ok cold. Anyone have any ideas what to do next beside buy a new one.

Art Mansfield
76 EL
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Re: [GMCnet] Onan [message #76005 is a reply to message #75986]

Mon, 08 March 2010 15:47

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

amansfield1104 wrote on Mon, 08 March 2010 12:29

Art,
There are two prime things that cause the "runs bad after warm up" syndrome.

One is exhaust valve lash. When the valve get hot, the seat load gets too low and the valve leaks - and that heats the stem more. check the valve lash before you do anything rash.

Another one is the ignition coil. Put an inductive pickup timing light on the engine and wait until the engine starts missing and see if flashes are missing - too. Old coils sometimes go open on the primary when they heat up.

Good Luck

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: [GMCnet] Onan [message #76013 is a reply to message #76005]

Mon, 08 March 2010 17:00

tphipps

Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL

Karma: 9

Senior Member

I vote with Matt. Ignition coil is where I would go first. Pretty easy to test, or just replace. Finding the coil might be fun.

Tom Phipps,
75 GMC

2012 Phoenix Cruiser model 2552 KA4CSG

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Re: [GMCnet] Onan [message #76019 is a reply to message #75986]

Mon, 08 March 2010 17:23

Mr ERFisher

Messages: 7117
Registered: August 2005

Karma: 2

Senior Member

might consider this

http://gmcmotorhome.info/generator.html#ALTERNATOR

and read the Duane Simmons writings
gene

On Mon, Mar 8, 2010 at 9:29 AM, amansfield1104@charter.net <
amansfield1104@charter.net> wrote:

> I have just replace the points ignition wires and plugs. I tried to adjust
> the carb but it did not help. The compression is 125psi on both cylinders.
>
> It ran ok until it warmed up. Then it starts missing. I took the cover
> off of the points and they look fine, no missing. I am waiting for it to
> cool off and see if it still runs ok cold. Anyone have any ideas what to
> do next beside buy a new one.
>
> Art Mansfield
> 76 EL
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
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 [message #76052 is a reply to message #76019]

Mon, 08 March 2010 22:36

jimk

Messages: 6734
Registered: July 2006
Location: Belmont, CA

Karma: 9

Senior Member

Now that were putting on more hours on them, valve adjustment might
be in order.

On Mon, Mar 8, 2010 at 3:23 PM, Mr.erf ERFisher <mr.erfisher@gmail.com> wrote:
> might consider this
>
> http://gmcmotorhome.info/generator.html#ALTERNATOR
>
> and read the Duane Simmons writings
> gene
>
>
> On Mon, Mar 8, 2010 at 9:29 AM, amansfield1104@charter.net <
> amansfield1104@charter.net> wrote:
>
>> I have just replace the points ignition wires and plugs. I tried to adjust
>> the carb but it did not help. The compression is 125psi on both cylinders.
>>
>> It ran ok until it warmed up. Then it starts missing. I took the cover
>> off of the points and they look fine, no missing. I am waiting for it to
>> cool off and see if it still runs ok cold. Anyone have any ideas what to
>> do next beside buy a new one.
>>
>> Art Mansfield
>> 76 EL
>> _______________________________________________
>> GMCnet mailing list
>> List Information and Subscription Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
>
> --
> 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
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
Jim Kanomata
Applied/GMC, Fremont,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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