Onan issue

LQQKatJon

LQQKatJon

Well-known member
Oct 22, 2010
3,208
527
113
St. Cloud, Mn
lqqkatjon.blogspot.com
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/
 
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

> 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:
>
 
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
 
Jon,

I do not know the Bovee ignition mod. If it still has a condenser, change that out. I have had several engines that had this condition and after I
changed everything else, I changed out that condenser (capacitor) and that fixed it. On one of them, the change was accidental and it wasn't until
later that I figured out what fixed it.

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
 
I concur. Had that same situation with the Onan one time.
bdub

-----Original Message-----
If it still has a condenser, change that out. I have had several engines that had this condition and after I
changed everything else, I changed out that condenser (capacitor) and that fixed it.
 
Mine did that a long time ago. Found out that the fuel system (tanks and filler) were so tight that air had trouble getting in to replace used fuel,
and the Onan fuel pump was not strong enough to over come the relative vacuum created by the running engine. Discovered the problem when I loosened
the gas cap and heard the woosh of air going into the tank. So, I loosed the gas cap and the Onan ran normally. JWID, so loosen the gas cap and try
running it for a while.
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
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/
 
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
 
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/
 
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

> 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:
>
 
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/
 
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
 
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/
 
> 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.

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? Fuel line collapsing? 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.
 
> > 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.
>
> 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. Seemed like it went slowly lean. 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.
 
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
 
Good call, Carl. Mine was a perforated fuel line. Started but wouldn't
maintain after it started. It was sucking air.

bdub

> 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.
>
 
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

> Good call, Carl. Mine was a perforated fuel line. Started but wouldn't
> maintain after it started. It was sucking air.
>
> bdub
>

>
> > 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.
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
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
 
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

> 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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