Onan 4000 Generator not quite starting - Probably a fuel issue

[uchu]

In your 4K genny, use cheap plain 30W engine oil. Any brand you want.

-Don- Reno, NV

Agreed. No point to overpay for "Onan" oil

 

[Tiercel]

BTW, the gap in the champion was significantly under .025". That was the smallest I Had within reach and it was not close to fitting the gap.

 

[Tiercel]

DonTom, the Amazon link you shared on carbs seems to be for Onan "K" and "P" series. I have a "J" series. Do you have a different model of Onan Generator? I might be doing something wrong because when I search "4KYFA26100J" I only get hits on NPN-"J" models.

The user ratings on that carb were not very reassuring. I will put a properly gapped new spark plug in tomorrow (if it hopefully stops raining). Maybe I will get lucky, and it will miraculously start. If it does, I will drop the fuel line into a jug of gasoline and SeaFoam to clean it out. I am not too optimistic, and I will order a carb from somewhere in the next couple of days either way.

 

[DonTom]

DonTom, the Amazon link you shared on carbs seems to be for Onan "K" and "P" series. I have a "J" series. Do you have a different model of Onan Generator? I might be doing something wrong because when I search "4KYFA26100J" I only get hits on NPN-"J" models.

My Y2K RV genny is a 4.0 KY-FA/26100 J. The exact same model as yours. And that is the one I ordered (twice now, as I just purchased a spare).

I learned a long time ago to ignore review ratings and for countless reasons, but I still read them because many of them have good info. But if you want to use the ratings, you have to know how to read between the lines. Such as the carb wasn't the issue to begin with, or the guy didn't know how to adjust it. I bet there are the same amount of complaints if you can search the Onan carb ratings somewhere.

But all I can say, is I only made minor adjustments to mine and it's never ran better (other than the Champion Spark Plug issue) with the cheap carb.

-Don- Reno, NV

 

[Tiercel]

My Y2K RV genny is a 4.0 KY-FA/26100 J. The exact same model as yours. And that is the one I ordered (twice now, as I just purchased a spare).
-Don- Reno, NV

Thanks, that's all I need. I just ordered one.

 

[Henry J Fate]

I did not see anything about a new air filter. Regardless of what it looks like, get a new one.

The only replacement air filter that I know of is the Onan/Cummins factory part. It's a little pricey somewhere around $15 last I knew. Onan/Cummins part # 140-3280 for the Microquiet 4K spec J.

My biggest problem with the air filter was the crankcase ventilation hose which dumps its guts into the air cleaner and craps it all up. I eventually disconnected that hose from the air box and placed the end in the engine area with some foam wrapped around it. I then bought a bag of heating register filter foam and wrap that around the filter to get more hours from the filter. I can replace the foam and use the same filter. I also apply a slight oil film over the foam to catch the small particles. It has been a welcomed addition with long filter life.

 

[Tiercel]

Henry, the air filter looks great but I will order one anyway. $15 seems pretty cheap at this point . I also thought about a fuel filter but if anything it is flooding fuel so the filter must be ok.

 

[Henry J Fate]

Fuel filter is a good idea. When I first bought my current winnebago with the 4K spec J less than 200 hours but sitting for years, I replaced the air filter, fuel filter, plug, changed the oil and removed the carb for a complete cleaning. At about 1000 hours or so I did the valves which was the best service I have ever done on the spec J. I assume the valves were outa spec from the beginning. The microguiet never ran so good. I will do it again at 1500.

Not to give the negative vibes on the replacement carb, I have never replaced a carb over the 50 years of working on small engines and motorcycles. Cleaning and an occasional float needle is all I have ever done. I assume it's alot easier to install a new carb for $40 rather than cleaning the old but I do think about the engineering involved and feel much better using the factory parts. I guess if I ever had to replace the carb on my spec J I would probably get the $40 one rather than pay Cummins for an over priced one.

 

[cully]

New member, first post.....love this site
I'm having very similar issues with my Onan as the OP, Tiercel. My hopes are Tiercel won't mind me poking and piggy backing my interest and concerns into his thread? Is there etiquette with this concern? Give it to me straight.

My Onan starts right up and runs strong for about 10 minutes then shuts down. Before it shuts down, at about 8 minutes in, it gulps a second then perks right back up for the last few minutes. Might it be best to follow along with this thread and start trouble shooting the same as Tiercel? I've called everyone in my area (Seattle) that I can find that works on Onan/Cummings. Either they ( boat yards) only work on diesels or RV businesses don't call back that say they do Onan service. The generator time counter on the toggle read 17 hours on it when i bought the RV this August. It now has 22. I have been exercising the generator almost daily once or twice a day since August. I guarantee I am the least mechanical member on the site but I'll keep after this issue one way or another.

The Rv is a 1992 Jamboree Searcher Special Searcher by Fleetwood. Clean and tight rig and all appliances work great. I've had to manual myself on most all appliances to troubleshoot. I'm very thankful the former owner keep ALL the manuals. They helped me get my feet wet.

 

[Henry J Fate]

One other note....

I switched to mobile Synthetic 30 weight oil. I figured for 1.6 Qts, why not use a good oil especially since it is air cooled. I just happen to use mobile because that's what I use in the car. I buy a 5 gallon container of it for $25. The car uses 3.4 gallons and the spec J uses 1.6. Perfect 5 gallons.

 

[Henry J Fate]

Cully, welcome.

I suggest to start a new thread. You will get plenty of help. Post the model number of the generator in addition to the info you posted here.

 

[Ex-Calif]

New member, first post.....love this site
I'm having very similar issues with my Onan as the OP, Tiercel. My hopes are Tiercel won't mind me poking and piggy backing my interest and concerns into his thread? Is there etiquette with this concern? Give it to me straight.

My Onan starts right up and runs strong for about 10 minutes then shuts down. Before it shuts down, at about 8 minutes in, it gulps a second then perks right back up for the last few minutes. Might it be best to follow along with this thread and start trouble shooting the same as Tiercel? I've called everyone in my area (Seattle) that I can find that works on Onan/Cummings. Either they ( boat yards) only work on diesels or RV businesses don't call back that say they do Onan service. The generator time counter on the toggle read 17 hours on it when i bought the RV this August. It now has 22. I have been exercising the generator almost daily once or twice a day since August. I guarantee I am the least mechanical member on the site but I'll keep after this issue one way or another.

The Rv is a 1992 Jamboree Searcher Special Searcher by Fleetwood. Clean and tight rig and all appliances work great. I've had to manual myself on most all appliances to troubleshoot. I'm very thankful the former owner keep ALL the manuals. They helped me get my feet wet.

Welcome aboard - I'd recommend you start a new thread for your issue.

This generator on this thread stops immediately after the start switch is released. A generator that runs 10 minutes will almost definitely be a different issue.

 

[cully]

Rodger Wilco, Thank you Ex-Calif

 

[Utclmjmpr]

Don Tom is wrong on the altitude setting,, when set to 10000 feet the fuel is LEANER to compensate for the thinner air at altitude,,so when at a lower altitude it needs to be RICHER ..>>>Dan

 

[Ex-Calif]

Don Tom is wrong on the altitude setting,, when set to 10000 feet the fuel is LEANER to compensate for the thinner air at altitude,,so when at a lower altitude it need to be RICHER ..>>>Dan

I was also gonna mention that.

So far all the tuning advice is nice but the generator is starting but as I read it, it is quitting when the start switch is released. This usually indicates a failsafe protect is not allowing the generator to keep running. Here are a few generic failsafe items.

1 - Oil pressure. Almost 100% of generators will shut down if no oil pressure.
2 - Start ignition - most generators are magneto. If the magneto is grounded it won't run. Some generators have a "shower of sparks" type system to facilitate the spark.
3 - Over/under volt. I would make sure the generator output switches are off. If it runs with the generator output isolated it could be a generator control/voltage problem.

You have to start closing in on why it runs with start button pressed and dies when released.

 

[DonTom]

Don Tom is wrong on the altitude setting,, when set to 10000 feet the fuel is LEANER to compensate for the thinner air at altitude,,so when at a lower altitude it needs to be RICHER ..>>>Dan

Yep. Easy for me to get confused these days in my old age.

Yeah, engines run richer at high elevations, so adjust the carb leaner up there with the higher elevation setting.

BTW, will the 6.5 KW genny in my new RV be fuel injected? I hope they are not still using carbs!

-Don- Reno, NV

 

[Utclmjmpr]

I don't know,, but probably not because it would have to have a high pressure pump to do that..>>>Dan ( I learned early on about the altitude thing as a commercial pilot for 33 years..)

 

[uchu]

So far all the tuning advice is nice but the generator is starting but as I read it, it is quitting when the start switch is released.

I missed this part. Yes, it might not be fuel related, after all.

While looking for "George", our coach, I almost ended up buying a different motorhome. This one had a Onan generator with the same issue. Running while pressing the start button.

I didn't buy it because some other issues with the coach, but the owner told me he ended up fixing the genny issue; it turned out to be a faulty voltage regulator.

 

[crawford 111]

I know when my Onan gave me trouble oil level was a little low added some back in business.

 

[Tiercel]

I am pretty sure it is the carb because if I give it a shot of starter fluid, it kicks off, but then gasoline starts running out of the carb. So my guess is a stuck float or something, probably from gasoline that turned to varnish sitting in an unused generator for years. I may have misled to say "it is starting until I release the switch." I can hear it firing and trying to start.

PS: My carb is supposed to come today, so when I saw the box I grabbed it and headed down to the MH, sat down by the generator, and opened it up. It was make-up my wife ordered. It was almost a youtube moment.