2019 Onan 4000 KY RV gas generator issues

[Db327]

I have an 18-month-old (2019) Onan 4000 KY (R) series gas generator that won’t run. We put 12 hours on the gen last year, no hours this year. When I tried to winterize & de-gum it 2 months ago, the gen wouldn't start at all. I’ve spent the last 2 months trying to get it running.

After spending way too many hours cleaning, removing, and soaking the old carb in carb cleaner (with limited success), I gave up and replaced the old carb with an after-market carb. I’ve successfully cleaned and rebuilt many other carbs and engines in my life.

With the new carb, the gen will run for 1-2 minutes unassisted while cold. When the gen gets warm, it stalls and won’t restart. However, if I manually hold the throttle open, I can force the gen to run for a few more minutes until it gets hot. Once the gen gets hot, it won’t start or run at all. When the gen is hot, it feels like the governor is pushing back against my attempt to hold the throttle open.

BTW, the gas is fresh, there’s plenty of gas in the tank, the fuel pump seems to work fine, the spark plug is clean, the air filter is spotless, and the oil level is correct. The gen behaves the same with or without a load. The RV & gen is only 18 months old!

I’ve read hundreds of posts on many forums about fixing this gen. I’m out of ideas.

I’d appreciate any help on what might be wrong and what to try next. Since I bought the new carb on Amazon, I can still return it and try an expensive OEM carb instead.

The behavior makes me wonder whether there are more issues beyond the carburetor.

Thanks in advance for your help!

Dave

[Down South]

I'm not sure. It sounds strange. Have you checked the fuel filter?
Or maybe you could disconnect the fuel line from the carb, stick it in a jug and hold the prime switch to see if you have good fuel flow from the pump?

[NackDSP]

The manual says to run this generator for something like two hours every month to keep it in good shape. When were these designed, 1955? That was a very disappointing thing to see when I read it, but that's what I'm doing. I would change the fuel filter and then check that everything in that carb has the varnish off of it and moves freely. Seems like it might be getting too lean. Certainly message Onan to see what they say. I'm planning to pull mine eventually and go with something much quieter.

[tap4154]

Does it show any codes when it stops? Also a common problem is the oil should only be just a little bit above the add mark. If you have it up to the full mark, the oil can expand and it will shut off from having too much oil.

But as others have said, you need to run that generator every once in awhile. You can't just let it sit for a year. Also check and make sure you have plenty of cooling exhaust coming out the bottom. Make sure you don't have a rat's nest up in there or something.

[OldWEB]

STANDARD THREE-YEAR LIMITED WARRANTY WITH AVAILABLE FIVE-YEAR EXTENDED COVERAGE
Why not let them worry if it is only 18 months old?

[Down South]

Originally Posted by OldWEB

STANDARD THREE-YEAR LIMITED WARRANTY WITH AVAILABLE FIVE-YEAR EXTENDED COVERAGE
Why not let them worry if it is only 18 months old?

We have a winner!!!

One note on those Chinese carbs. I had to replace one on my Yamaha ATV. The Chinese carb came with extra sets of jets.
If so, I wonder if you have the correct jets in it.

[Db327]

I contacted Onan/Cummins service before I touched it. Carb issues aren't covered under warranty. They want a 3-hour diagnostic fee at $172/hour. No thanks. I've seen other posts where they charged $2500 to replace a carb. They mark up a $350 retail carb by 2x.

We previously owned a class c for 6 years with a similar generator. No issues despite using it just occasionally.

Yeah, I see the recommendation to run it for 2 hours every month. That's just poor design!!! I don't have to run my lawn tractor every month, and it's 20 years old.

The most frequent code is 36... Fuel system. Sometimes it shows other codes. It seems odd that the new carb runs ok for a few minutes, but only when cold.

[THenne1713]

Loose connection/ intermittent power to the carb solenoid? Bad solenoid? Intermittent/ failing FUEL PUMP; (You may have that 1-2%, even if YOU replaced previous?)... WHAT did you find when cleaning/ repairing old carb?

[Isaac-1]

There is good reason for running it under load once per month, modern gasoline with ethanol added has a very short shelf life and is prone to gumming up carburetors, in addition to this tarnish tends to build up on the slip rings of the generator, if you allow it to get too bad it can burn out the voltage regulator portion of the control board. As to how long to run 20-30 minutes per month seems to be plenty.

[danhannah]

X2 on keeping the oil level at the very bottom of the dipstick. This cured my problem. Many were shipped with the wrong dipstick.

[OldWEB]

An odd warranty I would say, if they will not warrant a major part. Do you think a complaint to them would be in order?

They hide the actual warranty online, but you can find snippets...

Warranty Policy This limited warranty covers virtually everything except routine maintenance for the first two years you own your RV generator set, and covers parts and labor on major power train and generator set parts during the third year.

Also found:
Cummins utilizes the 4 C’s to guide our Service Providers through a successful warranty repair.

• Complaint
  A complaint is generated by Connected Advisor, a warning light, or a performance issue and the Customer is responsible for making the Product available for repair by a Cummins authorized Service Provider.
• Cause
  The Service Provider will use Cummins published Service Information to troubleshoot and perform failure analysis until the root cause and resulting progressive damage are identified.
• Coverage
  The Service Provider will then determine if coverage is available for the failure and to what extent it can be covered. Cummins reimburses for failures due to Factory materials and workmanship, failures and/or damage resulting from abuse or neglect are not covered.
• Correction
  Once responsibility is determined and the Customer agrees, the Service Provider will perform their correction of the failure. A Customer can incur charges during a warranty repair, but should never be charged an additional amount for a job covered by warranty.

[OldWEB]

Something else I found that may help:
GENSET STOPPED WITHOUT FAULT CONDITION – FAULT CODE 36
Possible Causes: Auto Gen Start (AGS), fuel supply, air fuel mixture, exhaust system, loads, Inverter/Charger, choke, demand regulator, carburetor, generator drive system, generator windings, ignition, wire connections

CHECK FUEL SYSTEM If the engine cranks and has spark but does not start, the problem is likely fuel related. This can be confirmed by injecting a small amount of starting fluid into the air intake.
If the engine fires and tries to run, it is starving for fuel. Listen for the fuel pump running during cranking. Check for 12 volts at the FUEL PUMP pin on the control board during cranking. If there is no voltage, the control board is defective. The pressure and flow of the fuel pump (and fuel filter) can be checked by temporarily disconnecting the fuel line to the carburetor and jumpering the FUEL PUMP pin on the control plug to battery positive. Take adequate precautions when handling fuel. If pressure and flow are normal, reconnect fuel line.
Note: If the generator has not been run for several months, the carburetor float may be stuck closed and /or the jets and needle valves may be gummed up by old fuel that has turned to varnish. These conditions interfere with normal fuel delivery. The automatic choke may be stuck closed or binding so that it does not open as the choke heater warms up. On Models BGM and NHM spec. B and later, make sure that the electronic governor goes to full throttle one second after cranking begins. Any of these conditions will prevent the engine from starting or running smoothly and must be corrected before proceeding.

[avfordguy]

I am assuming it ran fine before this issue came up. Code 36 is fuel system, replace fuel pump with an airtex from Amazon ( direct replacement). Onan 4k fuel pumps are terrible, no pressure or no volume, they are fine one day,yet the next day they sound like they are fine, but will not supply enough fuel to the carb. Easy test, hold stop button for 15 seconds, crank genset, if it runs and stalls, remove float bowl drain screw, fuel should run out for 30 to 45 seconds, if it does not, replace fuel pump

[cherv]

Whenever i can get non ethanol i fill the coach tank. Non ethanol fuel was recommended by our lawnmower service shop and what a difference in engine running.use it in home gen., snow blower been trouble free..