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Gen shuts off unless “Start” held down

TechMan101101
Explorer
Explorer
Hello All,

I have a 1999 Winnebago Minnie WF 331C and it has a Cummins Onan Model # FKY FA26100H generator that has 316 hours on it.

Issue:

Fuel pump ONLY has current when “Stop/Start” toggle is held down in the “Start” position.

In other words, the generator runs fine as long as I hold the “Stop/Start rocker switch in the Start position. I can even run it long enough for it to warm up.

As soon as I let go of the start switch power to the electric fuel pump is cut off.

I pulled the fuel line at the carburetor and fuel quantity and quality is fine but ONLY when the toggle is in the start position. NO fuel is being pumped when toggle is in the center (run) OR left “stop” position.

I have been reading a lot about this generator and researching troubleshooting docs and videos.

I am aware of oil level sensitivities…. Current oil level is at 1/4 on dipstick when cap is screwed in.

I am aware of vehicle gasoline fuel level sensitivities… Motorhome fuel tank is FULL.

Thanks in advance (Smile)
12 REPLIES 12

TechMan101101
Explorer
Explorer
Hello all,

I finally had a chance to run a couple of tests.

1) My generator runs GREAT as long as I keep pressing the “start” switch at BOTH the generator and inside the carriage. YES I understand that pressing the “START” switch keeps the starter engaged (that’s for those that want to warn me about possibly burning out the starter).
2) As soon as I let go of “Start” it just shuts off as if I am pressing “Stop”.

It turns out there is absolutely NO voltage output from the generator side of this Onan generator. The ENGINE side is working fine.

If I were still working as an ASE certified automotive repair technician I would take the generator out and rebuild it. But unfortunately I had to have both my hips replaced due to osteoarthritis and I just can’t get around like I used to.

MrWizard
Moderator
Moderator
Yes it is possible to have dirty slip rings on the FEILD ARMATURE (Not Stator he has the terms reversed) ,I used too have a burnishing tool that I used too clean the commutators or slip rings on motors, when servicing machinery,
And some times after setting for long periods unused the brushes stick in the holder and do not make good contact with the slip rings , then there is no power being applied to the armature field windings, feild voltage is in the 24v to 30v range to produce 120v in the output stator windings,
To damage the stator windings takes extended overload on the generator (usually during hot weather) that heats up the generator without drawing over load current that trips the breakers on the generator, that or a sudden massive overload like a dead short, or a crossed circuit with shore power, failed stators without this kind of crisis are very rare,
Stuck brushes, dirty slip rings, or loss of armature magnetism are 2,3,4 causes after #1 failed control board,
With Onan gensets if there is no 120v output the control board will not stay in run mode,
On occasion i have run into the situation where the armature has lost its residual magnetism (needed to start the process) and the generator needs to have this restored, i did this using a corded 120v electric drill,
The procedure is simple
Turn off all circuit breakers except for one that is for the outside or compartment duplex outlets
Turn on circuit breaker for external outside or compartment duplex outlet, make sure there is nothing else plugged into that circuit , plug in the drill (there is no power, it will not run) ,
Now hold the drills on switch on , use your other hand to spin the drill manually do this for several minutes non stop
Explanation
The drill is a permanent magnet motor, it will act like a DC generator,
Turning it by hand will output a low voltage DC current back thru the power cord and into the generator windings, sometimes this is enough apply a small magnet field allowing the genset to start producing power and eliminating the need to replace the armature which is the field windings,
So after spinning the drills motor several minutes, unplug the drill set it aside , and try starting the generator,
Unless i have my memories crossed ,
Maybe it should be noted
That in an AC generator such as this the field windings are in the armature which is turning (this can sometimes corrode)
The output Stator windings are the fixed windings around the the inside of generator head/housing, " they do not corrode "
In an electric induction motor, these 2 items are reversed the feild windings used to induce the armature to turn, the feild windings are the fixed ones and power is applied, the rotating magnetic field in housing fixed windings, causes the armature to turn and chase/follow the moving feild
Good luck
Clean the slip rings, check brush movent and contact , you can check b armature winding using a multimeter on ohms setting, test at the brushes and at the slip rings if possible, and infinite high reading is a problem , a low ohms continuity reading is good,
With generator running or held in start to stay running, you can check for feild voltage at the brush holders, DC volts between 20 to 30, No feild voltage means bad control board, proper voltage but no 120v output means no brush contact, or bad armature feild windings,
Or last case least likely damaged open output "stator" windings,

Nomeclacture:
Armature the part that turns
Stator the part that dies not turn
Feild windings
In a motor that is the stator
In a generator that is the armature
The feild can be stator or armature depending on if the device is a motor or a generator,
With a motor the feild is used to induce the turning off the armature shaft,
With a generator the turning of feild armature by a mechanical force, gas engine thus rotating the magnetic field,
Is used to create voltage in the fixed stator output winding,
In the typical electric drill with brushes and a "Commutator" the armature is energized with the power needed to attract the winding segments toward the magnets, making the armature turn, it works differently than your box fan induction motor which is the inverse of your generator, a Commutator is more complicated and troublesome than your box fan induction motor, but the drill uses this design because it produces more torque than a simple induction motor, and the drill needs this torque,
I hope i have not confused the issue. But i do believe your son's friend used the wrong term when he said failed stator, I'm sure he meant failed feild armature, but from what you posted , i don't think that is the the case,
I can explain it to you.
But I Can Not understand it for you !

....

Connected using T-Mobile Home internet and Visible Phone service
1997 F53 Bounder 36s

TechMan101101
Explorer
Explorer
Hey all,

I wanted to give everyone an update on my generator issue.

I haven’t been able to make any progress on it lately because of work obligations and lack of extra funds but my son in law has a friend that is manager at one of the main trailer and RV dealerships here in Portland Oregon.

I spoke with him the other day and he said he sees this all the time on Motorhomes that sit for a long time. He told me it is a dirty or corroded STATOR…. AND that he has a special tool for cleaning the stator without taking the generator out of the vehicle.

Is this possible on a 2000 Winnebago Minnie with a Cummins Onan Model # 4KYFA26100H generator? Has anyone heard of this? He said if his tool works great. If not, then the stator needs to be replaced which requires pulling the generator.

TechMan101101
Explorer
Explorer
Hello all,

I really appreciate everyone’s input and help. (Smile)

Unfortunately, my Onan generator model KY series H does NOT have a diagnostics code light as at least one person has pointed out. You guys ARE able to see the images of my genset, right? (Smile)

Also, they have pointed out that there is NO oil level sensor either. But just to be on the safe side… I will carefully increase the oil level to just below the “FULL” mark with the dipstick screwed in. This one does NOT make sense and I hope it is wrong??

Anyway, I found the COMPLETE FULL original manuals for my Motorhome. They are at least on the level of “Chilton” automotive repair manuals if not as good as “Mitchel” shop manuals; VERY detailed. They were in one of the cabinets and I hope I mentioned that I just bought this Winnebago a couple months ago.

We are having something called an “Atmospheric weather river event” (aka: constant rain) here in the Pacific Northwest and with my health AND my three part time jobs I will continue to diagnose this generator issue as soon as possible.

So next, what I am going to do is:
A: Carefully fill the generator oil level to just below full.
B: Using a long high quality extension cord and my digital VOM (Volt Ohm Meter) I will start the generator and see if there is at least 80 to 90 volts AC (alternating current). This is the minimum voltage that must been seen so it goes into “run” mode. Even better if my VOM shows 115-120 volts AC.

I just wanted to give everyone a heads up and let you all know I am still working on this.

When we get to the bottom of this I will treat everyone out to the beverage of their choice (smile)

(PS. To answer a couple of questions: My genset has 316 hours on it as I mentioned in my OP. (Smile). Also, thank you VERY much for pointing out how corroded the main 12 volt battery cables are at the solenoid…. I DO know the importance of having clean and tight battery cables. I will be splicing in and soldering a good length of brand new cable once I verify that the cost of getting this Gen to work properly is less then say $300. Because I can buy a brand new gas generator (Third party, NOT Cummins) for about $350. And although my battery cables at the Gen solenoid are terrible it cranks just fine.)

Thanks in advance, and I will keep everyone informed.

bounder39zman
Explorer II
Explorer II
your Onan 4KY spec H does not have a low oil level sensor, nor does the control board have fault code diagnostics. OP is probably correct, that generator is not producing AC power, which control board has to "see" to turn on run relay on board. Most common causes are bad field brushes or bad brush contact with rotor slip rings, bad voltage regulator, or bad control board. Worse case scenario is gen. rotor or stator shorted or open winding. Getting to field brushes is somewhat involved, as the fan/flywheel needs to be removed for access. Voltage regulator and control board are expensive items, so throwing replacement parts at it in an attempt to fix it can cost a bunch of $$$ and very possible would not work if brushes/rotor/stator are bad. Replacement control board and voltage regulator are available aftermarket from FLIGHT SYSTEMS in PA. Best bet is to find a qualified ONAN service to accurately diagnose problem. Good luck

ScottG
Nomad
Nomad
If an Onan quits running when the start button is released, it means the gen isn't producing power. If it's a newer unit, the starter will kick out and it will run as long as you keep the button pushed so someone can do some diagnostics - like check output voltage. It will not hurt the gen to do this.

MNtundraRet
Navigator
Navigator
The other post mentioned needed to have the control board replaced.
You might want to check the connections to the board first.
Mark & Jan "Old age & treachery win over youth & enthusiasm"
2003 Fleetwood Jamboree 29

wra
Explorer
Explorer
It could be the carburetor fuel shut of valve is stuck in the off condition. Follow the wires to the carburetor and it should lead you to the valve. Disconnect the wires, unscrew the valve. Clean and lubricate it so the rod moves easily. -OR- replace it with a new one.

jspringator
Explorer
Explorer
And make sure there is not too much oil in it. I don't fill mine to the full mark any more.
Jim & Sherri
02 Winnebago Sightseer 27c Class A;
"Scout" Springer Spaniel, gone but not forgotten;
"Boo" Chocolate Labradoodle.

eHoefler
Explorer II
Explorer II
First off fill it with oil to the full mark
2021 Ram Limited, 3500, Crew Cab, 1075FTPD of Torque!, Max Tow, Long bed, 4 x 4, Dually,
2006 40' Landmark Mt. Rushmore

wa8yxm
Explorer III
Explorer III
What is the fault code.. When it stops the light will flash (You can also initiate flashing I think by tapping the STOP button) count the nuber of blinks. It will flast 2 or 3 digits then repeat like 2 or 3 times.

If it's 32 than there is another thread on that problem elsewhere.
32 means "Battery low/Not cranking fast enough (officialy) but you know that's not the case since it ran.... Three people I know of had to replace brushes on the generator slip rings.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times

CA_Traveler
Explorer III
Explorer III
Is a fault code displayed?
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland

Bob