Home » Public Forums » GMCnet » Onan issue
| Onan issue [message #366486] |
Sun, 05 September 2021 16:45  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Generators and I do not get along.
Trying to help my friend ed with his onan. This thing has been kicking our butts for a couple seasons as well as a couple others who have tried helping.
Starts. Runs for a while. 5 min? Peters out. Will start and repeat when it cools.
Has newer(last couple years we have been tossing parts at it).
Fuel pump(oem airtex style).
Fuel hose
Fuel shut off.
Have rebuilt multiple carbs. This last carb came from jeff sirum- rebuilt.
Harley coil.
We just put in bovee ignition.
Oil level full. Lots of gas.
I am thinking we have a bad coil. Spark seems maybe weak when it shuts down and kinda erratic. Trying to watch it with a timing light. Spark never disappears but when it quits it will drop
To like 600 rpm for 20 seconds?? It indicates spark, but I think it should flash more.
Shooting starting fluid in to restart it does not seem to work. And plugs are not really wet.
Short of dumping the carb bowl. I am thinking it has gas. Take hose off and there is gas to the carb. Not vapor locked. (Was thinking it was a fuel issue, but replaced all that!).
I am wondering what powers the coil??? I am thinking that maybe I need to get a different power source to it(hotwire).
Man it now runs nice when it runs!
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| [GMCnet] Re: Onan issue [message #366487 is a reply to message #366486] |
Sun, 05 September 2021 16:59  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Coil would be my first guess. Gets hot and quits. Cools off and runs for a
bit. If you have Bovee's ignition, you have eliminated the ignition points
and poor primary ignition circuit. You might check your primary ignition
source conductor and connectors. If they are loose, they will exhibit
similar symptoms. No run when hot. Just what I would check. Sounds like you
have fuel system covered. If you have a GM upfitted coach, be sure you have
3/4 of a tank of fuel in the rear tank. That Onan fuel pump pickup only
goes part way into the fuel supply so you cannot use the Onan and run
yourself out of gasoline.
Jim Hupy
Salem, Oregon
On Sun, Sep 5, 2021, 2:45 PM Jon Roche wrote:
> Generators and I do not get along.
>
> Trying to help my friend ed with his onan. This thing has been kicking
> our butts for a couple seasons as well as a couple others who have tried
> helping.
>
> Starts. Runs for a while. 5 min? Peters out. Will start and repeat
> when it cools.
>
> Has newer(last couple years we have been tossing parts at it).
>
> Fuel pump(oem airtex style).
> Fuel hose
> Fuel shut off.
>
> Have rebuilt multiple carbs. This last carb came from jeff sirum-
> rebuilt.
>
> Harley coil.
>
> We just put in bovee ignition.
>
> Oil level full. Lots of gas.
>
> I am thinking we have a bad coil. Spark seems maybe weak when it shuts
> down and kinda erratic. Trying to watch it with a timing light. Spark
> never disappears but when it quits it will drop
> To like 600 rpm for 20 seconds?? It indicates spark, but I think it
> should flash more.
>
> Shooting starting fluid in to restart it does not seem to work. And
> plugs are not really wet.
>
> Short of dumping the carb bowl. I am thinking it has gas. Take hose off
> and there is gas to the carb. Not vapor locked. (Was thinking it was a
> fuel issue, but replaced all that!).
>
> I am wondering what powers the coil??? I am thinking that maybe I need
> to get a different power source to it(hotwire).
>
> Man it now runs nice when it runs!
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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| Re: Onan issue [message #366488 is a reply to message #366486] |
Sun, 05 September 2021 17:37 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Meter for 12 at coil/pump (same circuit). My guess is a bad solder on back side of board. See if Voltage goes away or weak when it dies. Use clip leads and meter or a small light bulb would be easy to watch. Betting on a bad solder ( dull ring of death) on back side of board. Besides the relays, the actual Faston tabs can have it as can fuse holder. Examine under magnifying light.
If this only happens when drawer closed, it’s pinched fuel line to tray barb.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Onan issue [message #366493 is a reply to message #366486] |
Sun, 05 September 2021 20:52 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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This is a friends coach that I help maintain. I do not get enough time with it to really diagnose things properly. He is retired so will swap out and do many things so hard to chase down issues.. my onan is parted down now, so I took the bovee kit off mine and installed it on his. I was not really aware exacty what it was doing. I thought the carb he got from sirum and a couple gmc’rs had it running well at last
Rally. But it turns out they got it running good..
Adjusted the carb, generator, ect. But it still had this shutdown issue.
Watching the voltage to the coil is what I should of done today.
Will see about that capacitor, that should be easy too.
I thought it was a pinched fuel line. But today I crossed that off. Does same pushed in or pulled out and pulled out I can see fuel line is not pinched. (Newer lines).
Thanks.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Onan issue [message #366496 is a reply to message #366493] |
Sun, 05 September 2021 21:36 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Jon,
Have you bypassed the board (jumper from 9 - 5)? How about the LOP switch, if bad, that would shut the gen off after about 5 minutes?
Otherwise, John L may be on to something with the kinked fuel hose suggestion.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Onan issue [message #366772 is a reply to message #366486] |
Tue, 14 September 2021 12:19 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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the onan saga continues.
sucker still shuts down.... most parts new. Our next thing is to try Another new coil, and a new condenser on the coil.
we ran it off a small boat tank, still quits after 5-10 minutes. does that pulled out or pushed in.
jumpering the coil off the battery does not help. also shows good voltage to the coil the entire time, and the timing light seems to show spark, but when it dies the rpm reduces and it kinda misses a little bit, so the timing light flashes a little erratically, but I still think it has spark to match? we are trying new plugs, need to get some new plug wires. I just realized I was only testing the timing light flash on one side of the coil, not the other....
the fuel shut off is new, but also was not in the loop when we ran it on the boat tank.
been pretty busy, so having a hard time really sitting down and thinking right on this. I know people install a doorbell transformer when some windings go bad?? does that effect how the engine runs, like if those windings dump when it gets hot that would cause it to shut off?
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| [GMCnet] Re: Onan issue [message #366773 is a reply to message #366772] |
Tue, 14 September 2021 12:35 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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I know you’ve been chasing this awhile over several threads. Did you ever
obtain Duane Simmons Onan troubleshooting chart? I don’t recall seeing that
you had gone through it in the thread(s)
Sully
Bellevue wa
On Tue, Sep 14, 2021 at 10:19 AM Jon Roche wrote:
> the onan saga continues.
>
> sucker still shuts down.... most parts new. Our next thing is to try
> Another new coil, and a new condenser on the coil.
>
> we ran it off a small boat tank, still quits after 5-10 minutes. does
> that pulled out or pushed in.
>
> jumpering the coil off the battery does not help. also shows good
> voltage to the coil the entire time, and the timing light seems to show
> spark,
> but when it dies the rpm reduces and it kinda misses a little bit, so the
> timing light flashes a little erratically, but I still think it has spark
> to match? we are trying new plugs, need to get some new plug wires.
> I just realized I was only testing the timing light flash on one side of
> the coil, not the other....
>
> the fuel shut off is new, but also was not in the loop when we ran it on
> the boat tank.
>
> been pretty busy, so having a hard time really sitting down and thinking
> right on this. I know people install a doorbell transformer when some
> windings go bad?? does that effect how the engine runs, like if those
> windings dump when it gets hot that would cause it to shut off?
>
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: Onan issue [message #366774 is a reply to message #366486] |
Tue, 14 September 2021 14:13 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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Been going through alot of the troubleshooting guides multiple times. This is a multi-year project. common to tear into Ed's Generator at a Rally to eventually end up at a list of things to try. Then those things get tried and problem still there. It is just cursed!
I should also mention it has a dinosaur board. We did toss a new board at it at one point.
I don't understand the condenser situation. The bovee gets ride of the one that should sit next to points, but there is one that hangs on the coil, and that is the one that is next on list to swap out. Ed was trying to figure out where to buy and what part number for that one. I am sure venders have it, but would take a week to get at this point. sometimes the local RV places that service onans can get them quick.
I re-read what sully stated, and I think I will have to get some light bulbs hooked up to some wires with alligator clips. Would be good to watch a light bulb on the power feeding the fuel pump. too bad they don't make a see through float bowl.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Onan issue [message #366775 is a reply to message #366486] |
Tue, 14 September 2021 14:54 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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METER for 12V+ at coil + with a clip lead. If it stays there at same level when it dies, you do not need to throw a board at it.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Onan issue [message #366780 is a reply to message #366775] |
Tue, 14 September 2021 17:59 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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Board was a few years ago.
Last weekend test showed good voltage at coil. As well as timing light flashing away. Also ran jumper to coil from battery and it still died.
Today hooked up pin9 to 5. Ran it and it died same way.
Again seems there is fuel. This is like the 4-5th carb rebuild and 3rd carb. This carb was sent down and rebuilt by jeff sirum. And he said he ran it on an onan and it worked fine.
I think it might be flooding itself out??? But i dont think the spark plugs really look wet.
Trying to hold open carb butterfly does not let it really restart. You just have to walk away for 5-10 minutes and it will start up and run again.
I am thinking of holding a contest and offering $$ reward to anybody at gmcmi who can get this bugger to run for over an hour straight.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Onan issue [message #366784 is a reply to message #366780] |
Tue, 14 September 2021 19:43 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Senior Member |
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lqqkatjon wrote on Tue, 14 September 2021 17:59Board was a few years ago.
Last weekend test showed good voltage at coil. As well as timing light flashing away. Also ran jumper to coil from battery and it still died.
Today hooked up pin9 to 5. Ran it and it died same way.
Again seems there is fuel. This is like the 4-5th carb rebuild and 3rd carb. This carb was sent down and rebuilt by jeff sirum. And he said he ran it on an onan and it worked fine.
I think it might be flooding itself out??? But i dont think the spark plugs really look wet.
Trying to hold open carb butterfly does not let it really restart. You just have to walk away for 5-10 minutes and it will start up and run again.
I am thinking of holding a contest and offering $$ reward to anybody at gmcmi who can get this bugger to run for over an hour straight.
I stood next to that thing and watched it while it slowly died. My gut feeling from observing and smelling the exhaust is that it is a fuel problem. If the carb ran good on another Onan, look up the line. Fuel pump? It is electric and could be failing as it heats up. Fuel line collapsing? Pick-up in the tank plugged? Just seemed fuel to me, and considering you saw the timing light flashing as it quit....kinda illuminates spark. JWIT
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
[Updated on: Tue, 14 September 2021 19:44] Report message to a moderator |
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| Re: Onan issue [message #366790 is a reply to message #366785] |
Wed, 15 September 2021 10:57 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Two additional potential problems come to mind:
Fuel inlet in tank plugged as Larry suggested = starving for fuel. Try blowing air through the line back into the tank with the gas cap off.
Too strong of a fuel pump, should be 2 - 3 PSI = flooding out as it gets hot.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| [GMCnet] Re: Onan issue [message #366792 is a reply to message #366790] |
Wed, 15 September 2021 11:04 |
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Good call, Carl. Mine was a perforated fuel line. Started but wouldn't
maintain after it started. It was sucking air.
bdub
On Wed, Sep 15, 2021 at 10:57 AM Carl Stouffer wrote:
> Two additional potential problems come to mind:
>
> Fuel inlet in tank plugged as Larry suggested = starving for fuel. Try
> blowing air through the line back into the tank with the gas cap off.
>
> Too strong of a fuel pump, should be 2 - 3 PSI = flooding out as it gets
> hot.
>
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bdub
bdub.net
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| [GMCnet] Re: Onan issue [message #366794 is a reply to message #366792] |
Wed, 15 September 2021 11:31 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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I believe that he stated earlier that he set up an alternate fuel supply (
separate fuel tank and line) and the problem remained unchanged.
Sully
Bellevue wa
On Wed, Sep 15, 2021 at 9:04 AM Billy Massey wrote:
> Good call, Carl. Mine was a perforated fuel line. Started but wouldn't
> maintain after it started. It was sucking air.
>
> bdub
>
> On Wed, Sep 15, 2021 at 10:57 AM Carl Stouffer wrote:
>
>> Two additional potential problems come to mind:
>>
>> Fuel inlet in tank plugged as Larry suggested = starving for fuel. Try
>> blowing air through the line back into the tank with the gas cap off.
>>
>> Too strong of a fuel pump, should be 2 - 3 PSI = flooding out as it gets
>> hot.
>>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Re: Onan issue [message #366798 is a reply to message #366794] |
Wed, 15 September 2021 16:23 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Good point, Sully. Fuel starvation must not be the problem, at least not due to a restriction in the pick-up.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| [GMCnet] Re: Onan issue [message #366800 is a reply to message #366798] |
Wed, 15 September 2021 16:55 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I have had many years of experience with air cooled, valve in block
engines, and over time I have encountered several instances of expanding
engine blocks that "used up" all the valve to valve tappet clearance when
they got hot. This would prevent the valve, or valves, from opening fully
and no fuel mixture or not enough fuel mixture could enter the cylinder.
Then the engine acts like it is running out of gas, which it is, but for a
different reason. One of my John Deere riding mower with a Kohler engine
did this, and it took me quite a while to figure out what was going on.
Cure? Grind a bit more clearance off the end of the valve stem. Worked for
me.
Jim Hupy
(Retired Vocational Instructor in Small Engines and Power Mechanics)
Salem, Oregon
On Wed, Sep 15, 2021, 2:23 PM Carl Stouffer wrote:
> Good point, Sully. Fuel starvation must not be the problem, at least not
> due to a restriction in the pick-up.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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