2015 an up Onan 4000KW models 4KYFA

[Luke D]

I have found out through Onan and several certified service techs that on these models the oil level or oil sensor was eliminated. The provision on the control board is bypassed. Another interesting thing I found out from Flyght systems is their replacement control board has eliminated the code system. So mode flashing codes when this board is used. Another thing I learned was in order to get to brushes or clean stator the engine must be separated from the generator. Totally enclosed on newer generator s.
The service techs here in Tampa at Cummins Onan swear the newer generation 4000KW have several bugs. They are backed up for months on generator repairs.
Yes mine still not fixed. Haven’t had a chance to bring home and pull out. Still only runs when you push and hold start button. Hopefully this weekend. Looks like my job to fix. Every shop booked for months. Plus original repair service won’t touch generators any more. Lazydays, Camping World and General RV here locally booked for months and not interested in the work. RV Medic will look at it once out and I bring it to them. Let’s hope I can fix.
Stay safe

Just up dating all

Luke

[Mr Sunshine]

Good luck to you! Let us know what the fix is.

[Luke D]

Originally Posted by Mr Sunshine

Good luck to you! Let us know what the fix is.

So the Onan generator problem resolution. On all 4KYFA26 models grounding is critical. Your fuel solenoid must have a tight ground. Mine was loose and stripped. Next grounding lug on bottom of left front side of pan is prone to corrosion and vibrates loose. This is wear your main batteries negative lead connects. I redid ground and tightened. Now the fault. What happens as ground is not steady the voltage regulator in the control board fails due to erratic contact. Voltage dropping and starting again. Unfortunately the cheaper Flight System replacement board fails way sooner than the Onan board. The Onan board, much more expensive , will send out a code if voltage dropping. Flight System’s board has no code provisions. Lesson learned. Onan fixed.
Last issue never fill oil to fill line , leave at least a quarter above first line. Your generator will never cut out running till you turn off.

Luke

[BeardyMcWeirdy]

Luke, It sounds like I may have a similar issue as you. Did your generator spit out any fault codes? I have a 2018 Onan KY but it is spitting out a "4-8". Generator field sense. Can't find anyone online with experience with this code

[Luke D]

Originally Posted by BeardyMcWeirdy

Luke, It sounds like I may have a similar issue as you. Did your generator spit out any fault codes? I have a 2018 Onan KY but it is spitting out a "4-8". Generator field sense. Can't find anyone online with experience with this code

Mine had an after market Flight Systems control board, their board will not display codes. Flight System’s eliminated the code error system on all their boards. Needless to say I re- installed an Onan OEM board.
My experience with code 48 is a field voltage issue. Now can be corrosion on slip rings, bad brushes and believe it or not there is a way to adjust field voltage. Your control board regulates the 12 volts needed to run not field voltage . Your field voltage is the 110 the generator sends to power your RV. The engine requires 12 volts to run engine. The conversion another control board function Does generator run ?
Or only run when switch is held?

[BeardyMcWeirdy]

Understood.
Yes I’ve always taken fault codes with a grain of salt, since they’re designed to direct you to the culprit, but regularly I’ve found that the solution is a little less direct. (;
The generator only fires up for 1-2 seconds then shuts down. It always fires up in the first 1 or 2 cranks - which suggests to me that the spark/fuel/air is there, but then something else jumps in and kills it.
Also, it shuts down whether I’m holding the start button or not.

[Luke D]

Originally Posted by BeardyMcWeirdy

Understood.
Yes I’ve always taken fault codes with a grain of salt, since they’re designed to direct you to the culprit, but regularly I’ve found that the solution is a little less direct. (;
The generator only fires up for 1-2 seconds then shuts down. It always fires up in the first 1 or 2 cranks - which suggests to me that the spark/fuel/air is there, but then something else jumps in and kills it.
Also, it shuts down whether I’m holding the start button or not.

Suspect either fuel cutting off or fuel solenoid voltage is cutting off. It’s easy to check fuel, disconnect fuel line from carb, press prime not start. Have line in cup , should shoot out nice spurts. Solenoid must have constant 12 volts on start and run. That fact that yours starts but dies guickly seems issue maybe elsewhere. Unfortunately control board sends voltage to both once started. In order to stay running generator has to be supply power to the board. In start mode battery power starts engine. Board is by passed. How many hours on generator?
Was it running fine? Has it been sitting long?
Mine did the same once and it was my carb. My last failure was electronic. Needed to say I’m not a big Onan fan. Especially the newer 4000 KY series. They don’t even have an oil sensor or oil level sensor. Now they will shut down on low oil pressure or will all of a sudden die if over filled. My friend Kevin works at Cummings Onan here in Tampa. Their booked solid. With generator repairs. He showed me a unit where critters actually chewed wires and the 12 volts for running was shorting to ground. He calls today’s units junk. Oh well , got to have a generator.

Luke

[BeardyMcWeirdy]

Hey Luke,
Just wanted to give you and everyone else an update.

As you suspected, it was the control board. The unit was firing up without a problem. That told me I was getting fuel and spark. But it would shut down after 2 seconds maybe.

I ordered a replacement control board, plugged it in, and she ran great.

Crazy because it’s a 2018, garage kept, with 150 hours. Hard to believe the board could go bad that quickly.

Thanks to your help, I was able to diagnose the problem quickly, correctly, and get it taken care of.

Big thanks to you Luke for sharing your knowledge. It saved me a ton of time, effort, and money.

I owe ya

[Luke D]

Originally Posted by BeardyMcWeirdy

Hey Luke,
Just wanted to give you and everyone else an update.

As you suspected, it was the control board. The unit was firing up without a problem. That told me I was getting fuel and spark. But it would shut down after 2 seconds maybe.

I ordered a replacement control board, plugged it in, and she ran great.

Crazy because it’s a 2018, garage kept, with 150 hours. Hard to believe the board could go bad that quickly.

Thanks to your help, I was able to diagnose the problem quickly, correctly, and get it taken care of.

Big thanks to you Luke for sharing your knowledge. It saved me a ton of time, effort, and money.

I owe ya

Great news . Glad your back up an running. The control board is the heart and soul. Of course the hardest to diagnose, but unfortunately a common issue. Heck even if you see codes none tell you control failure.
Be safe an enjoy.

Regards
Luke

[John & Diane]

Luke,


Thanks for the interesting information. Our coach was built in March of 2014 and titled as a 2015. Out of curiosity, I looked up the spec sheet for our model 4KYFA26100. s/n 4KYFA26100P, and there is no mention of a low oil shut off feature. I think this missing feature goes back to at 2014 or earlier.
Thanks to you, many of us will be more diligent on checking the oil level! Thanks again.

[Luke D]

Originally Posted by John & Diane

Luke,


Thanks for the interesting information. Our coach was built in March of 2014 and titled as a 2015. Out of curiosity, I looked up the spec sheet for our model 4KYFA26100. s/n 4KYFA26100P, and there is no mention of a low oil shut off feature. I think this missing feature goes back to at 2014 or earlier.
Thanks to you, many of us will be more diligent on checking the oil level! Thanks again.

Great, our coach was built on a 2014 chassis but also a 2015. From my findings The Model 4KYFA started eliminating oil level or oil pressure sensors around late 2013. Onan had so many problems with that feature it was discontinued. The engine is similar to a lawn mower design. Oiling is done with a flinger ( slinger) which splashes oil inside block. Thus no filter , no pump. Now running low on oil it can overheat and should shut off from the heat but my guess is it will fail with internal damage. Crazy…. So check your oil level, leave a little below fill mark. Too much oil will shut down to. It will restart but with to much oil run times vary from minutes to an hour. Another thing to remember is use a quality 15/40W oil. Change every 50 to 75 hours or once a year. Don’t waste money on synthetic.

Be safe Enjoy

Luke

[Chateau_Nomad]

Interestingly we're seeing other generator brands (Yamaha) being installed in new motorhomes. Supply chain shortages?? I thought Onan had a lock on the RV generator market. I have an Onan 4k (QG something) on a class C... about 3 years old. Have had zero problems so far.

[Luke D]

Originally Posted by Chateau_Nomad

Interestingly we're seeing other generator brands (Yamaha) being installed in new motorhomes. Supply chain shortages?? I thought Onan had a lock on the RV generator market. I have an Onan 4k (QG something) on a class C... about 3 years old. Have had zero problems so far.

Great, it’s like a car, same model, make and year some fine some a lemon. Onan has had the market for years. Now with the Fallout with China and Korean parts, Onan facing a demand issue. Good to see Yamaha in there. Hope Honda gets involved in RV gen sets. One player never a good thing. The cake walk Onan has is always a downfall in quality.
Time will tell

Be safe Enjoy