New Onan 4000 wont start

[awesomeman]

Hi. I’ve got a Winnebago 2018. Our generator has about 30 hours on it and was last used about 60 days ago. Everything worked fine. I went to crank up the generator today and it cranks, starts, and then immediately shuts off. After that it only cranks but will not start. It also didn’t sound like it stalled out. Sounded like it was shut off. Here’s what I e tried. It’s a Cummins Onan 4000
1. Oil was recently changed before last use and oil level is accurate
2. Primed the lines for 30 seconds as mentioned in manual
3. Tested fuel lines. Fuel pump is working and pumping fuel just fine.

What are the common early failure parts on these generators. It’s so weird since it is newer. Nothing should be failing at this point but these things happen. I know on my last generator the oil pressure sensors were notorious.
Any help is appreciated as I’ve literaly owned the rv just over a year and the warranty is out. Lol.
Thanks

[Richmcm]

I had the same problem with my new MH back in 2006. Would start up and run for a minute and stall out. I would have to wait several hours and it would start again and stall again. It turned out being a carb float issue.

[bobndot]

I tend to agree on the carb. If any type of gasket needs to be replaced, make sure it gets installed the correct way. Sometimes is hard to tell, I learned the expensive way to the tune of $450 on a boat generator having the same symptoms. Had to call a factory tech who knew exactly what it was. Reversed the gasket.
It's funny, when I had genny problems while on the road, a repair shop offered me help as long as it wasn't an Onan. He said he refuses to work on them any more. He gladly worked on my Honda which I always carry as my backup genny and has become my primary unit to take care of my boondocking charging needs because it's more quiet. $35 and 45 minutes for the repair.
I do alternate running both genny's just to keep the fuel in circulation.

[bounder39zman]

Onan standard warranty on consumer products is 2 years or 2000 hrs, plus an additional third year on major components. fault code 36 is displayed when gen slows down or stops without a command from control board or stop switch (usually fuel related) code 15 is low frequency/speed.
Sounds like you have carb problems, will need cleaned or replaced. Of course, Cummins-Onan does not consider a gummed up/varnished carb to be a warrantable issue

[Ponderosa]

Sure sounds like a gummed up carb. You can't leave it for 60 days with gas in it and not expect problems. Two weeks is about it. Buy a new one or take the old one off and put it in a gallon of ChemDip carb cleaner overnight. It's a bit of a pain to get off but it can be done without taking it out.

[Gjac]

I assume it has spark because it starts, I would still pull a plug and see if the spark will jump at least 1/4 in to ground and is nice and bright to rule out ignition problems. I would then disconnect fuel line to carb remove air cleaner and spray gas or carb cleaner into carb and see if it stays running if so I would suspect a fuel delivery problem. I have had two intermittent problems that drove me crazy like that. One was just a bad 12v connection to the fuel pump, the other was the pick up tube going to the fuel tank. I am sure yours in not cracked or rotted but it can be loose do to someone not tightening the hose clamp. Also you can remove the jets and spray the holes. You manual will tell you how many turns to open each one as an initial setting. Being this new I would think it is something simple. Also try disconnecting the sensors to see if that helps. If you try these things and report back you will get better suggestions.

[awesomeman]

New update. I drained the carb. Got it to crank up but was rough idle. Actually not rough as it was pulsating. It stalled out after 5 minutes and now stalls right out after starting. Going to try more carb cleaner and clean the fuel lines. Got code 15 and 36. Any input?

[youracman]

Ooops! Should say ".....whilst cranking it" Getting late....past my bedtime. lol

ed s

[youracman]

awesomeman wrote:
Well fudge me.....changed spark plug, oil, and air filter. Nada. Trouble code 36. All leads and voltages are solid. Cmon guys I need some ideas

The only time my 4K Onan cranked but refused to start, it turned out to be the magneto. I discovered the bad mag by holding the plug against the Onan body (cooling fins IIRC) whilst it ..... no spark. A new mag assembly and it has run fine ever since. But then mine is 12 years old; has approx 500 hours on it and had lived down near the Calif beach for a several years before I bought it (the OEM mag turned out to be very corroded.)

Even though your Onan is almost new by comparison, I would VERIFY it has spark. If it passes the spark test, at least you know you probably need to concentrate on fuel delivery (and not just to the carb inlet....to the cylinder.)

Just my $.02

Good luck......know it is frustrating.

[bukhrn]

Probably means nothing in your case but, on our first trip to Yellowstone, our Onan started, then quit, did it a couple times, while looking around, I noticed the altimeter setting was set at the lowest setting, in Yellowstone we were at 6000ft +/-, soon as I reset it to 5000+ it started & ran without a problem. :h

[awesomeman]

Well fudge me.....changed spark plug, oil, and air filter. Nada. Trouble code 36. All leads and voltages are solid. Cmon guys I need some ideas

[D_E_Bishop]

Just one step in troubleshooting would be to check and verify that the generator is putting out 120vac. I have a 5.5K so I do have an outlet, if you don't, It is simple to remove the cover from the ATS and hook a meter to the cables from the generator and see if the generator is outputting and eliminating geting into the guts of the thing.

Doing that would eliminate one big possible problem.

If the generator is not generating 120 vac, the generator engine will not run, so check that the delay circuit is receiving power. As DrewE said there will not be any power to the system until the delay circuit closes and pulls in the ATS but the generator produces power as soon as the engine starts. Actually it starts producing power as soon as it starts turning. That is one of the first things the tech in the authorized shop did when mine failed.

What you have done is to make sure that the generator is outputting. Like I said, mine was not and threw a code 32, Low Oil.

[awesomeman]

Read the fault code. Its a code 36. At least it doesn’t seem like a major code. Says to check fuel level, air filter, and spark plug and to check for mechanical damage

[youracman]

mgirardo wrote:
We had an issue with our brand new Onan in our 2009 Class C. Ours didn't even have 10 hours on it. My wife fired up the Generator while I was driving. She tried to heat something in the microwave for 1 minute, but the generator quit after 30 seconds or so. Restarted it and it quit again shortly after start up. Then it never fired up.

The error code, which I do not remember, basically translated to "have generator serviced". It turned out to be a fuel pump that the dealer replaced under warranty.

I would contact Cummins and find out what the warranty of the Generator is. It maybe more than 1 year as previously mentioned. They should also be able to help troubleshoot over the phone or email. Or at the very least find the nearest authorized repair facility.

-Michael

Good example of an "early failure part" the OP asked for, Michael. Wow! 10 hours!
He apparently removed the fuel line from the carb and verified fuel flow though, as he stated that his fuel pump was working.

'Twill be "velly intellesting" to find out what the cause of his failure was. Hope he reports back. These Onans can drive ya nuts at times.

Best......ed s

[mgirardo]

We had an issue with our brand new Onan in our 2009 Class C. Ours didn't even have 10 hours on it. My wife fired up the Generator while I was driving. She tried to heat something in the microwave for 1 minute, but the generator quit after 30 seconds or so. Restarted it and it quit again shortly after start up. Then it never fired up.

The error code, which I do not remember, basically translated to "have generator serviced". It turned out to be a fuel pump that the dealer replaced under warranty.

I would contact Cummins and find out what the warranty of the Generator is. It maybe more than 1 year as previously mentioned. They should also be able to help troubleshoot over the phone or email. Or at the very least find the nearest authorized repair facility.

-Michael