Home » Public Forums » GMCnet » Onan runs like sheet!
| Onan runs like sheet! [message #76267] |
Wed, 10 March 2010 14:21  |
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well dont know whats up with the onan, has maybe 15 hours on i since I installed the new points and she ran fine. then just the other day for what ever reason it starts stuttering, skipping and stammering but not stalling. I checked the plugs, points, oil, and even adjusted the carb but no dice...
WTF is wrong with it now? arg....
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: Onan runs like sheet! [message #76268 is a reply to message #76267] |
Wed, 10 March 2010 14:24  |
LNelson
Messages: 335
Registered: December 2008
Location: Springfield, MO
Karma: 0
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I have had good success pulling the jets and spraying carb cleaner in and out. Put the jets back in and........all is well. Cheap to try.
Larry Nelson Springfield, MO
Ex GMC'er, then GM Busnut
now '77 Eleganza ARS WB0JOT
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| Re: Onan runs like sheet! [message #76270 is a reply to message #76267] |
Wed, 10 March 2010 14:31 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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| Duce Apocalypse wrote on Wed, 10 March 2010 15:21 |
well dont know whats up with the onan, has maybe 15 hours on i since I installed the new points and she ran fine. then just the other day for what ever reason it starts stuttering, skipping and stammering but not stalling. I checked the plugs, points, oil, and even adjusted the carb but no dice...
WTF is wrong with it now? arg....
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Sir: it might be low on gas? most GMC built coaches have to have 1/4 tank or more for the Gen to pick up fuel??
C. Boyd
76 Crestmont
East Tennessee
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| Re: Onan runs like sheet! [message #76275 is a reply to message #76267] |
Wed, 10 March 2010 15:27 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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I concur. it is likely sucking air into the carb due to low fuel int he bowl or possibly the carb is loose and vibration is causing the carb to wobble, suck in air a the manifold thinning out the mixture. Had a Briggs powered McClane Lawnmower with that problem until I re-engineered the carb mount.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: Onan runs like sheet! [message #76277 is a reply to message #76267] |
Wed, 10 March 2010 15:47 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Duce Apocalypse wrote on Wed, 10 March 2010 15:21 |
well dont know whats up with the onan, has maybe 15 hours on i since I installed the new points and she ran fine. then just the other day for what ever reason it starts stuttering, skipping and stammering but not stalling. I checked the plugs, points, oil, and even adjusted the carb but no dice...
WTF is wrong with it now? arg....
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When you don't know, do the whole diagnosis before you do anything (to the engine, a popping a beer does not count).
Fuel, Ignition and Compression
Does it have spark? - Yes you say you checked the points and plugs, but did you actually check that there is spark - it runs badly, so there probably is - but check that because it is easy.
Is it getting a good solid fuel feed? This is harder to check, but a cheap and dirty way is to jury rig a piece of clear line between the pump and the carburetor inlet. If you see anything but solid fuel - fix that.
Compression is hard to check on most things, but not here. Unscrew the plugs and put the wires back on but leave them clear of the holes. Put a thumb in one hole and push the go button. When it blows your thumb out of the hole, change holes.
One of those tests will fail. Then, you fix that.
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 runs like sheet! [message #76296 is a reply to message #76277] |
Wed, 10 March 2010 20:32 |
amansfield1104
Messages: 80
Registered: August 2009
Karma: 0
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Mine is doing the same thing.
Art 76 EL
On Mar 10, 2010, at 3:47 PM, Matt Colie wrote:
>
>
> Duce Apocalypse wrote on Wed, 10 March 2010 15:21
>> well dont know whats up with the onan, has maybe 15 hours on i since I installed the new points and she ran fine. then just the other day for what ever reason it starts stuttering, skipping and stammering but not stalling. I checked the plugs, points, oil, and even adjusted the carb but no dice...
>>
>> WTF is wrong with it now? arg....
>
> When you don't know, do the whole diagnosis before you do anything (to the engine, a popping a beer does not count).
>
> Fuel, Ignition and Compression
>
> Does it have spark? - Yes you say you checked the points and plugs, but did you actually check that there is spark - it runs badly, so there probably is - but check that because it is easy.
>
> Is it getting a good solid fuel feed? This is harder to check, but a cheap and dirty way is to jury rig a piece of clear line between the pump and the carburetor inlet. If you see anything but solid fuel - fix that.
>
> Compression is hard to check on most things, but not here. Unscrew the plugs and put the wires back on but leave them clear of the holes. Put a thumb in one hole and push the go button. When it blows your thumb out of the hole, change holes.
>
> One of those tests will fail. Then, you fix that.
>
> Matt
>
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumiere (say show-me-air)
> SE Michigan
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: Onan runs like sheet! [message #76306 is a reply to message #76267] |
Wed, 10 March 2010 21:35 |
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The tanks are both at 3/4 so fuel is not a problem. I will check the carb and see if that is an issue.
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: Onan runs like sheet! [message #78297 is a reply to message #76267] |
Sun, 28 March 2010 14:13 |
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Well after more screwing around with the Onan this weekend, im beginning to lean to the coil being the issue. when I attach my digital timing light to the onan, and watch the RPM, I notice when it starts stumbling the tach reading ranges widely from 500 rmp to 3800 and everywhere in between before going back to around 1890 (normal no load)
I've literally been throught the carb 3x, put a new fuel pump on, and checked everything else and thats the only thing I can think of thats left.
I noticed a member also recommended cleaning the heads, I would try this too, but who sells new head gaskets?
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] Onan runs like sheet! [message #78310 is a reply to message #78297] |
Sun, 28 March 2010 15:49 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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Don't need new head gaskets, Just spray them a good coat with
aluminum paint.
J.R. Wright
GMC GreatLaker
TZE Zone Restorations
77 Eleganza Custom (For Sale)
1975 Avion (Under Reconstruction)
Michigan
On Mar 28, 2010, at 3:13 PM, Shan Rose wrote:
>
>
> Well after more screwing around with the Onan this weekend, im
> beginning to lean to the coil being the issue. when I attach my
> digital timing light to the onan, and watch the RPM, I notice when
> it starts stumbling the tach reading ranges widely from 500 rmp to
> 3800 and everywhere in between before going back to around 1890
> (normal no load)
>
> I've literally been throught the carb 3x, put a new fuel pump on,
> and checked everything else and thats the only thing I can think of
> thats left.
>
> I noticed a member also recommended cleaning the heads, I would try
> this too, but who sells new head gaskets?
>
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Onan runs like sheet! [message #78327 is a reply to message #78310] |
Sun, 28 March 2010 18:21 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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Several coats. Many coats. Lots of coats.
On Sun, Mar 28, 2010 at 1:49 PM, John Wright <powerjon@chartermi.net> wrote:
> Don't need new head gaskets, Just spray them a good coat with
> aluminum paint.
>
>
> J.R. Wright
> GMC GreatLaker
> TZE Zone Restorations
> 77 Eleganza Custom (For Sale)
> 1975 Avion (Under Reconstruction)
> Michigan
>
> On Mar 28, 2010, at 3:13 PM, Shan Rose wrote:
>
>>
>>
>> Well after more screwing around with the Onan this weekend, im
>> beginning to lean to the coil being the issue. when I attach my
>> digital timing light to the onan, and watch the RPM, I notice when
>> it starts stumbling the tach reading ranges widely from 500 rmp to
>> 3800 and everywhere in between before going back to around 1890
>> (normal no load)
>>
>> I've literally been throught the carb 3x, put a new fuel pump on,
>> and checked everything else and thats the only thing I can think of
>> thats left.
>>
>> I noticed a member also recommended cleaning the heads, I would try
>> this too, but who sells new head gaskets?
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> List Information and Subscription Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: Onan runs like sheet! [message #78334 is a reply to message #76267] |
Sun, 28 March 2010 18:45 |
Ernest Dankert
Messages: 133
Registered: May 2007
Location: Ogden, New York
Karma: 1
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Senior Member |
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How about the condenser? Condensers will break down with heat and probably less bux than a coil. I read all the comments in this string and did not see a reference.
1977 Eleganza II
Ogden NY
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| Re: Onan runs like sheet! [message #78375 is a reply to message #78334] |
Sun, 28 March 2010 22:01 |
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Points or coil condenser? points and points condenser were replaced less then 20 hours ago. coil condenser OTH is as old as genset. hmmmm yeah condenser is cheap enough like $12, I can try there first...
| Ernest Dankert wrote on Sun, 28 March 2010 18:45 |
How about the condenser? Condensers will break down with heat and probably less bux than a coil. I read all the comments in this string and did not see a reference.
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73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: Onan runs like sheet! [message #78390 is a reply to message #76267] |
Mon, 29 March 2010 02:39 |
Rusty
Messages: 197
Registered: October 2005
Location: Philadelphia Pa
Karma: 0
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Senior Member |
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I guess the Onan's are pot luck, some people's work fine for years, others have nothing but troubles. I fought with mine for 4 years before I yanked it and put in a Microlite 2800. Smooth sailing since.
Rusty
75 Glenbrook
Philadelphia Pa
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| Re: Onan runs like sheet! [message #78423 is a reply to message #78390] |
Mon, 29 March 2010 11:05 |
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mine also ran trouble free until recently, which indicates to me some kind of component failure. the problem is figuring out which component!
| Rusty wrote on Mon, 29 March 2010 02:39 |
I guess the Onan's are pot luck, some people's work fine for years, others have nothing but troubles. I fought with mine for 4 years before I yanked it and put in a Microlite 2800. Smooth sailing since.
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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! [message #78425 is a reply to message #78423] |
Mon, 29 March 2010 11:15 |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Senior Member |
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My Onan ran perfect the first 2 years I had my coach and then in spring of the 3rd year it ran like garbage. Finally found a loose gas line connection, it was sucking air. Put on new fuel lines, filter, etc and it again ran perfect.
Just some additional input.
Have a great day !!!
Ray
Ray & Lisa Erspamer
78 Royale Center Kitchen
TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMC-Royale@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/
________________________________
From: Shan Rose <defconfx@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Mon, March 29, 2010 11:05:05 AM
Subject: Re: [GMCnet] Onan runs like sheet!
mine also ran trouble free until recently, which indicates to me some kind of component failure. the problem is figuring out which component!
Rusty wrote on Mon, 29 March 2010 02:39
> I guess the Onan's are pot luck, some people's work fine for years, others have nothing but troubles. I fought with mine for 4 years before I yanked it and put in a Microlite 2800. Smooth sailing since.
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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List Information and Subscription Options:
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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| Re: [GMCnet] Onan runs like sheet! [message #78715 is a reply to message #78425] |
Wed, 31 March 2010 10:54 |
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yep I replaced all the lines and filter about a month ago, so I know thats not a problem.
I think its a carburation problem, ive got the onan carb broken down soaking in a pale of carby dip.
I replaced the plugs and noticed the old ones are very sooty with black soot, much more so then the normal amount, so I know its a fuel issue most likely.
im gonna order a new set of head gaskets and decarbonize the heads as well. hopefully this mini overhaul gets'er done. overall the onan has been quite reliable, its just learning to trouble shoot the little quarks of this actually very simple engine thats the problem...
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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