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Old 09-21-2021, 07:48 PM   #1
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onan 6500 cranks but only running on one cylinder

1999 winnebago brave 35 onan 6.5NHEFA26100P new control board , coil , plug wires , plugs , fuel pump , fuel pump filters , 653 hrs on genset , carburetor rebuilt .
I did this work last month on genset , have 3 1/2 hrs on it since. ran flawless until today . decided to crank generator while on a drive today to exercise generator . rode about half hour with generator and ac running . went home parked under shed, turned ac off , let generator run for about 5 minutes not loaded , then shut it off . opened compartment door to check generator , decided to start it one more time , will not start . tried to start it several times ,it did run on one cylinder a couple of times . at wits end with this generator , don't know which way to go now , any suggestions would be greatly appreciated ! thank you ! Russ
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Old 09-22-2021, 10:03 AM   #2
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Pull the spark plug boot on easiest one to reach.. see if runs.. process of elimination.. that will tell you which one..
SO guessing.. bet you pinched plug wire.. or did not seat boot.. let's hope..
Could be sticking choke.. maybe you did not get choke relay on..
Make sure full tank

Now my story... on an 5500.. 275hrs 2000.. so did almost exactly same thing.. tuned up.. cleaned carb.. and all back together run beutifull.. tried to restart .. ran as if one cylinder..
Tried everything.. retraced all steps.. replaced fp, still ran on 1 cylinder.. read here hours to days.. started losing hair, lost religion.. then ran across post here.. about critters.. so following hard fuel to tank.. it transition to rubber hose over top of tank to tank pickup... I had to use cell phone with camera and flash and record way up.. over tank.. I used a special scope camera to find out that critters ate tiny chunk out of fuel line..
Just enough not to leak, and gen worked beutifull when tank was full.. but as fuel level in tank dropped a little... the hole, the friendly critters left, would suck air.. it took me months to get to bottom of it.. then.. found clamp they used at factory was rusted out.. then found the rubber fuel line was cracking and hard.. just plain bad..
You could just try to adjust main jet.. to.. maybe gen sucked up a little trash in carb.. so try that sense it easiest ..

But when things go haywire and don't make sense keep critters in the back of your mind all the time..
Good luck and let us know what you did and maybe better members then me will help you

Also.. members here post.. hook gen up to 5gal gas can.. see if runs.. that is easy to try.. use all safety precautions..

THANK YOU.. TO ALL MEMBERS AND THEIR FAMILIES... that make posts and pictures.. I almost trashed gen.. over 10.00 fuel line.. so thank you all..
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Old 09-22-2021, 10:09 AM   #3
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Pull the rocker arm covers and see if all is well.
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Old 09-22-2021, 10:46 AM   #4
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Quote:
Originally Posted by donr103 View Post
Pull the spark plug boot on easiest one to reach.. see if runs.. process of elimination.. that will tell you which one..
SO guessing.. bet you pinched plug wire.. or did not seat boot.. let's hope..
Could be sticking choke.. maybe you did not get choke relay on..
Make sure full tank

Now my story... on an 5500.. 275hrs 2000.. so did almost exactly same thing.. tuned up.. cleaned carb.. and all back together run beutifull.. tried to restart .. ran as if one cylinder..
Tried everything.. retraced all steps.. replaced fp, still ran on 1 cylinder.. read here hours to days.. started losing hair, lost religion.. then ran across post here.. about critters.. so following hard fuel to tank.. it transition to rubber hose over top of tank to tank pickup... I had to use cell phone with camera and flash and record way up.. over tank.. I used a special scope camera to find out that critters ate tiny chunk out of fuel line..
Just enough not to leak, and gen worked beutifull when tank was full.. but as fuel level in tank dropped a little... the hole, the friendly critters left, would suck air.. it took me months to get to bottom of it.. then.. found clamp they used at factory was rusted out.. then found the rubber fuel line was cracking and hard.. just plain bad..
You could just try to adjust main jet.. to.. maybe gen sucked up a little trash in carb.. so try that sense it easiest ..

But when things go haywire and don't make sense keep critters in the back of your mind all the time..
Good luck and let us know what you did and maybe better members then me will help you

Also.. members here post.. hook gen up to 5gal gas can.. see if runs.. that is easy to try.. use all safety precautions..

THANK YOU.. TO ALL MEMBERS AND THEIR FAMILIES... that make posts and pictures.. I almost trashed gen.. over 10.00 fuel line.. so thank you all..
thank you for your suggestions donr103 . i have checked all that you suggested , have found nothing yet . this mourning i ran a jumper wire from positive cable running to the gen to the positive side of coil , it started after a couple times. i then pulled off jumper wire it ran for a couple minutes , coughed a couple times, backfired , then quit . tried to start it again , no luck . i'll keep after this thing until i get it running !!
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Old 09-22-2021, 11:00 AM   #5
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Originally Posted by twinboat View Post
Pull the rocker arm covers and see if all is well.
thank you for your response twinboat. i understand how the rocker arms will definitely mess this motor up, my question is why all of a sudden i can't get any spark when i take plug out & ground it then spin it over . i don't want to pull this genset out but it might be coming to that !
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Old 09-23-2021, 09:10 AM   #6
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Hold off on pulling gen.. TWINBOAT.. is a great members and with his help and my ,mis-guidance .. we can get you a few test to run yet..
So.. try starting at gen.. and keep holding down on start switch even after starts and see if runs.. hold maybe 30sec or so...Does it run?

When is last time you checked slip rings, the copper looking rings on ameture of gen part..? Are they nice and shiny ? Shine very good flashlights in there..

Shine very good on brushes.. can you see some?

I guess you could have bad, control board, or voltage regulator.. but there are test you need to do... 1st test coach batteries.. charge them up.. then try starting..
Next.. look in manuals.. see if testing/ trouble shooting guide for your model..

Use all safety precautions.. air cleaner off and hold choke open with something that will not get sucked in.. spray starting fluid into carb while cranking and see if runs

If still problem.. I would disconnect all neg on batteries and unplug rv.. gently pull control board.. look for spider webs, they can short board.. inspect board.. members here post... connection get corroded over time and need cleaning up.. and harnesses pins.. Does yours have codes you can get.. some newer ones do?

Next.. there are all kinds of test you can perform on harness and board.. I just can't remember them.. so .. you tube flight system gen repair.. MAYBE TWINBOAT .. can help.. or he can link all the testes..

I still guess that you have bad voltage regulator.. but you got to do a little testing 1st.. do you know where voltage regulator is?
SO you tube. And . get in manual for your model and look for testing procedure..
Good luck and let us know what you did and maybe better members then me will help you
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Old 09-23-2021, 07:10 PM   #7
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donr103
thanks again ! i did look at slip rings yesterday , very shiny, going to pull brush holder & inspect brushes tomorrow . today i ran voltage test on positive side of coil while i cranked it . i'm only getting 9.7 volts . i believe i should be getting at least 12 v . will have to do some more research to see what that reading should be . i'm getting no spark at plugs, checked by spark tester and also took plug out ,grounded it , cranked gen , nothing . plugs have 3hrs on them , will buy new ones . trying to find info on running diagnostic tests on control board, although i just replaced it . i have inspected all wires & voltage reg. in control board compartment , actually pretty clean , no broken or chewed wires , all pins in control board look good & tight . i'm trying to find a shop manual for this gen model # 6.5NHEFA26100P SPEC P is hard to find info on . hopefully i can find an actual shop manual that a tech would use , hopefully i'll be able to understand it if i find one ! its getting to be a challenge now ! i'm retired what else do i have to do !! thanks again !
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Old 09-24-2021, 01:04 PM   #8
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There are lots of video on you tube.. should be close.. onan gen repair.. also Google flight system gen repair.. great company.. make sure when measuring volts at coil you are holding down switch at gen.. I believe control board controls starting volts at coil.. can you try old board? YOU ARE GETTING FUEL RIGHT?
Then if control board does not see volts from armature it shuts off.. so it sounds like to me.. you bypass the pos on coil and got it to run some.. did it ever run right ?
Call flight system.. they can help.. do you have point type eng or non point type.. you can look on top and tell.. ? Do you have a bore scope camera.. ? If not they are cheap..
SO if non point type..you might have to jack down to get in there..some members post here.. you can loosen the bolts.. remove just the 2 in front and rock it gently to get to top cover off.. but still use all safety precautions.. and keep a jack and cribbing under it..
Then remove the top cover.. then remove the sensor on top that makes it fire.. THIS IF YOU CAN'T GET IT TO RUN ON BOTH CYLINDERS.. then you are going to have just love this.. use bore scope camera to find the plastic shaft on eng flywheel.. that tell sensor to fire each cylinder.. blasted critters get in there and nest.. look for that. If you see a nest or something.. hole thing comes out for repair.. there are great vids on this.. parts are cheap and its not that hard
Good luck and let us know what you did and maybe better members then me will help you
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Old 09-24-2021, 01:05 PM   #9
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Oh.. don't be afraid of reaching out to TWINBOAT .. direct.. just send him a message.. LETMEGROW is good too.. I was Hoping they would chime in
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Old 09-24-2021, 04:42 PM   #10
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Thanks again for reaching out ! i did hit start button while checking voltage at coil . I got a PDF shop manual from Cummins Tech Support . Old-Biscuit suggested i call them , talked with Ken , very helpful . It will take me a bit to take all this in but so far , there are a lot of tests i will be attempting before i take gen out !! there is a test for ignition module that i will attempt . I am leaning toward the module right now causing my issue. I really don't have to take anything apart for the test just un hook some wires off coil & hook my volt meter up , it is much more detailed than that but it will give me a direction to go ! i can get to the wires of the ignition module without any trouble. if that checks out , then i know the plastic prop on crankshaft with the magnets is not broke ! this will be a slow process , electrical troubleshooting is not my cup of tea !! i will learn ! i have some honey-do's to catch up on this weekend , Happy Wife-Happy Life ! will get back at it Monday. Thanks again , Russ
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Old 09-25-2021, 08:46 AM   #11
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Happy trails.. sorry forgot to mention OLD BISCUT.. there are so many great members here.. just hard to remember them all.. thank you.. just take your time.. you got a real good gen.. most here post they can go up to 30,000 hrs.. we will be long gone by then.. good luck and keep us posted
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Old 09-25-2021, 11:15 AM   #12
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What type of ignition do these gennies have? If magneto ,all it takes is small bit or rust or steel bit on flywheel magnet or magneto cores to break/short air gap and kill spark. Or short on primary side of magneto coil/s or wires to act like a kill switch. Some equipment engines have small cover to clean or sand the flywheel just so not to further have disassemble motor.
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Old 09-26-2021, 02:56 PM   #13
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best i can describe this ignition system is very similar to electronic ignition systems of the 70's ! instead of distributor it has what i call a propeller with magnets mounted to the crankshaft that spins across an ignition module that in turn that distributes the spark to the two plugs . good point on rust & dust debris will ground out a spark . Thank you for your input much appreciated !
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Old 09-26-2021, 04:23 PM   #14
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Remove the ignition pick up.. it's on the top. But under cover between eng and gen.. there is you tube vid on this.. onan used weird plastic paddle device that has two impeller to trigger spark.. critters nest inside gap between eng and gen part.. and nest or crap .. snaps impeller.. so you get one dead cylinder... this is where you use a bore scope camera to find out that critters were inside.. I have been trying on mine to scope this space without pulling gen to make sure it's clean.. I have been unsuccessful as of this time..

But if you bypassed ignition and got it to run ok.. and then cut out.. I can't see the above is your problem... if control board does not see gen make voltage it will suppose to shut down.. at least that is what I understand.. good luck and keep us posted
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