How to replace (or remove for repair)the carburetor on a Cummins Onan RV generator QG 4000 

Unsure on the costs of labor that your video saved me, thanks a lot. 😁

THANK YOU. Huge help - whoever asked what size that socket was - bless you! 10mm - for the long bolts. Simple replacement - $48 started first try!

The permanent fix for Onan generator problems is to add a shut off valve before the carb and run it dry after use. This way the carb (or a new carb or the one after that.....) does not get gummed up.

Thanks for this video. I was going to try running seafoam through it but I think it’s best to just replace. The previous owners hardly ever ran the gen so I’m guessing it’s pretty gummed up. Best to replace and properly maintain the new carb. I’m basically a rookie so this was super helpful!

Thanks! I thought I was missing a bolt on the right side but your video showed the bolts come in through the air filter housing and run all the way through to the intake manifold. Just what I needed and also where to tighten those bolts. Perfect!

First of all your video was extremely informative. If I may make a suggestion (based on watching you and myself remove and reinstall the carburetor) to facilitate in the removal and installation process. I made, out of scrap wood, a block to compress the foam gasket on the air filter housing. This minor addition compression allows just enough space for an easier removal and installation.

This has got to be the least friendly carburetor I’ve ever worked on. Thanks for the tutorial and honesty about these being non serviceable.

Thank you very much for your thorough video!! I’m no mechanic, that’s for sure!! I gotta say the information you discussed, and the video combined was enough for me to successfully accomplish the task!! Thanks again! Now I’m gonna try changing the oil next!

Fantastic job in showing how to do this.

I watched this video because I have an issue with the wires. I decided to send you and email and explain it better. I hope you can help. You have a nice channel here. Gary

Thanks for the video, It was very helpful. I changed my own and it's running fine. Getting the gaskets in was a bit tricky. I ended up putting the new carb in place and then slipping the gaskets in. If you push opposite directions you can get a little space and slide it in. Also used my phone camera to see where I was going when putting the bolts in or out, as you really can't see back in there otherwise.

Hey kb great video . Thanks for sharing. Take care & stay safe .

Super helpful thanks.

Nice video next time though start it up after 🙌🏾

Enjoyed this one. Didn’t know that the carbs were not serviceable. Invaluable info!

Merci très bonne démonstration accomplie par un pro...

Found the exact video but I was hoping you’d mention the size socket we’d need haha

Very nice work in that tight space. Keep it up brother!

Thanks for the instructions! Would you know the size socket the 2 bolts are that secure the carb? It's really difficult getting in there to size it! Thanks!

Good one KB, having fun on the road? It does put a little extra jingle in ya pocket.

So before buying a new carb, just clean the old one. It appears to come apart like any other and I suspect that some spray carb cleaner or brake kleen would do the trick nicely. Most likely it is just varnish in the float bowl and jets. If not keep and clean old one for next time.

Thank you for the video. Does the float bowl come off? Mine sat for a year without being run. On my last RV, I only had to remove the bowl and clean it and that solenoid out and it fired right up. Was hoping I could do the same with this 4000 too.

I had a RV shop replace a carb. Several yeas ago. $300+ . Going to try it myself. Ordered an after market one.

Awesome, man. I'm doing this today and my new carb kit also has a fuel filter. I guess you don't usually do that at the same time?

Wish you talked more. Idiots like me want to know what's holding up the process or what size bolt or dangers. Thanks. Altitude adjustment? Where?

THIS IS HOW I FIXED MINE, IN THE CASE OF.... "I CAN'T START MY GENERATOR" It's has been two years since last time it was running, so I started by checking oil level full at gen dipstick (it won't start if low oil because of sensors) then I checked gasoline more than 1\4 tank in the RV (also safety sensors), sparkplug checked for good spark, also checked the manual reset circuit braker ( to be ON) at front motorhome engine compartment for 12v current to the generator to be able to start it, also cleaned the carburetor and even installed new one but same situation, then checked wires and found some has been chewed like gum by rats at the back of starting switch generator panel so I replaced them, at this time the generator started but stay running only by keep pushing the switch on all the time, so then finally I knew it was internal electrical problem from the engine itself, so I took the generator out from my RV to work in my garage, (I did this by myself with some tools and old Mayan tricks ) lol, it's really heavy for one person. I disassemble the unit at my garage and started by removing the cover, then the cooling fan or flywheel unit (it's 2 items in one) until finally I was at the gen rotor and brushes assembly area and this is what I found: one more wire chewed by filthy rats plus the stinky rat nest in the middle of the generator motor coil, I fixed the wire and sanded the commutator copper contacts where the brushes are sitting becouse they were real duty with old urine from the rats, and of course I got rid off the stinky nest, lol!!! Then I assembled everything back together and... bingo it's runing like a champion!!! For this project materials involved was about $60.00 including an aftermarket new carburetor and an harmonic balancer/steering wheel puller (available at any auto parts for $25.00) to pull the aluminum fan out and (flywheel). Just picture this: (Any gasoline engine run smooth if gasoline and DC current aren't interrupted) so following this important principle you'll always find the problem to be fixed. Also if you have a onan microlite 4000 like mine, don't run it for more than a minute without the cover because you'll cook the engine real fast, also keep the eye on the aluminium fan and your fingers after cranking it in case you missing one or two members...just kidding, lol!!! After testing the gen with the help of a gasoline container, a piece of hose and 12v battery, I did put the air cooling assembly back and the rest of components including the cover, then it was ready to be installed at my RV. Once the gen was installed back at my motorhome I started it to be tested for 120v electricity but not before flipping the AC circuit switch (on) at the gen starting control panel (sometimes hiding under or around the panel) to be able to transfer power to my RV GFCI main outlet and electric panel as well, my motorhome it's equipped with GFCI so I reset it and tested for green led light indicating power is ready at my main breakers panel, so I turned my main breaker (on) along the others ones but no power was present at my breaker main switch (faulty main braker) so I flipped it many times, sometimes you can make it work again, mine did work, lol!!! I'm happy because everything works now including the refrigerator for cold drinks and AC for this crazy summer, lol! Later I'll buy me a new main braker, for now this is a resurrected generator story that needed to be shared. If this can help eaven one person to save time and $$$ it'll make me more happy, thanks for reading!!!

10 mm heads on the bolts, correct? I swapped mine out, thanks to this video, with relative ease. I didnt tighten the ground wire enough; most likely finger-tightened until I could get the proper bit in my screwdriver, which I obviously forgot. After a few trips and a few hours it was behaving as if it was again gunked up.

Wait did the new carb come with the wiring? I bought a Cummins OeM one. Do I have to swap out the solenoid with the wiring??

Job well done once again Kile

Did you ever retrieve the wing nut for the air filter housing top? I had to take the control board out to get to mine.

Nice video! We have to replace the carb on our Jayco. Same QG4000 generator. Generator sat too long and carb gunked up. My bad. Looks like this should be about a 45 minute job or so for an experienced tech, which we have. Just don’t want to hear that it was a 2 hour job at $150 an hour. Also, did you say that you used an after market carburetor? If so, can you tell me what brand(s) you like. My folks want to get one from Cummins/Onan, but they are about $500. I know they’re good, but are they 8 times better than the $65 after market imports? Thanks again.

I greatly appreciate this video! My QG4000 wouldn’t start after sitting a while. Since I had spark, i replaced the fuel filter and pump with no success. The carburetor is next but I’ve not seen any error code and that worries me. Is there something else I should check?

Great video, did it run after all that? I was going to Buy a can of seafoam and some gasoline and try to clean the carburetor manually but then I seen somebody bought a aftermarket carburetor $50 so I decided it would be cheaper in the long run to buy a aftermarket carburetor and install it on my Oman 4000. Just waiting for the carb to be delivered then I will attempt to install it. $15 for a can of seafoam then $5 or so for a gas can then the gas and a gas hose is half the cost of a cheap carburetor, just to try and clean the carburetor and then not work. Thanks again for the video.

Hello, I just got a 1997 Leprechaun RV and I think the unit has been sitting for a while. I'm trying to get the Generator to work but so far it will only run off of Starting Fluid. It's a Onan Microlite 4000 series. It has a Clear Fuel Filter underneath and so far I'm getting No gas out the Line . The Motor home Has 3/4 tank of gas in it . Do you have any ideas of which direction I should be looking at . Carburetor, Fuel Pump, the Fuel Line itself ??? Thanks for any suggestions. John.

Where did you source the new carburetor from?

What size socket to get carburator bolts out.

Nice job

The air cleaner bracket broke and I have a replacement coming. If I remove the carb can I put the new one in from there? Thank you in advance!

I have rebuilt quad carbs on motorcycles, & carbs on cars. Use an ultrasonic cleaner with eg. Simple Green. They come out like new.. Not sure why this carb can't be cleaned & rebuilt, though they are cheap to buy new.

KB did you put on gasket sealant on both gaskets? Do you need to do that? If so what type of gasket sealant?

Nice video, I purchased a non oem carb and had it replaced but to get it to start and stay running I have to manually pull out the throttle with my finger. Do you know why that might be happening? The guy who installed it does not know why it's like that either. Thank you!

Not much room in there mind but good video KB

Can you said where do you got the carburetor from...eBay .. Amazon and how much you paid for...you have a link for the buy...a new Onan carburetor is over $400 now ...

Size socket to remove the carb, would help!!

Thank you for the video. I have a question if you could help, my air filter bracket snapped and I have the part and I'm trying to replace that. It looks like I need to pull out the carburetor to do that. Is that correct?

How much do you charge to change out the carb?

KB what do charge for a mobile visit not including parts? Is it a flat rate or do you add on for mileage? Great video and an opportunity to expand on your core business.

Any word on where to get the replacement carburetor?

I have the same generator - just outta curiosity, did you check the error code, was it 36 - aka fuel related? I'm tempted to install a fuel cutoff valve on this, after i fix mine, to run it dry before storing, have you had any luck with that?

What was the size of socket you used to remove 2 bolts?

Would you please provide a link to the replacement carburetor for the Onan 4000 generator?

I just changed the carb on mine and when I try and start it it spits out a ton of fuel and won't run at all

Greetings, Does this have a kit to convert to propane? Thanx, -keith

Great video KB also got some of my stickers on the way shoot me an email and I'll get them out as soon as I get them

Where does that spring go.

Left or right lever

An you do this on the 2500 propane model?

It is all about cost vs. benefit.

I have a 2.8 onan and its totally different

Anyone knows the part number for the Carburetor? Ive got a local place charging me $950 for the part.

Where do I get a replacement?

Who news Cummins and Carb go in the same sentence😂

you skip the most important part which is what size those 2 bolts are

I had a guy who called me on. Saturday afternoon wanting the fuel pump and filter changed on one of those to be ready for a Monday morning cross country trip!! Onan I said? Ya right!!!