Onan 4000 watt RV generator Repairs, Service, and Common Problems 

Thanks for NOT including background music over your narration!

Why do they say must run the generator once a month(?) the Gas will dry out of the carb. and the fuel pump will not operate with the engine not running one must disconnect the fuel pump wire run it to a twelve volt and fill the carb. first.

You do damn good quality work!!! Very detailed!!

Thanks so much for what you do for all of us viewers! Love your stuff.

I got tired of replacing nearly $400 carbs so I went with an Amazon carb. It's been 3 years, so far so good. At the time I couldn't find a carb and figured I would only be out of $30.Honestly I think the biggest fix was the in-line fuel shut off. I run my generator once a month and after an hour, open the compartment and cover and shut off the fuel. It runs dry in 2-3 minutes and fires right up next time around. If I'm out using it I don't bother until we are packing up. I wish I had put the in-line shut off in when my generator was new, it probably would have saved a lot of money and headaches.

I'm 60 years old and every time I see you do work like this I feel that I should be right there next to you helping you up at least holding the camera 😊✌🏽

Excellent video! Really appreciate you taking the time to film this! Now I know how to service my Onan 4000 Generator

So nice to see the proper steps. Thank you so much!

Great video content James! I just did a tune up on my 1995 Winnebago including spark plug. The oil was nasty black like it had not been changed in years! It has white smoke until it warms up. Was thinking of trying some Lucas leak stop! Do you have any suggestions for possible leaking valve seals?

Great video as always. I found something that might be really helpful. Last year my Onan 5500 wasn't running right so I removed and cleaned the carburetor only to have the same problem this year. After watching countless videos I finally found this on RU-vid, "Updated Onan Marquis Gold 5500 Generator How Stop Carburetor Surging Without Removing Carburetor." In the video he removes the plastic cover that restricts the main jet altitude adjustment range . I carefully pried off the plastic cover without removing the carb.and unscrewed and cleaned the jet needle. I screwed it in until it was fully closed and then opened it 3 turns. It started right away and his rich/ lean adjustment procedure got it running perfect. Without the plastic cover you can adjust the jet and compensate for manufacturing tolerances and varnish buildup. Maybe everyone is replacing Onan carburetors because they get a little varnish and there is not enough adjustment range so it runs too lean. I just could not accept that such a simple carburetor could go bad and have to be replaced.

You cna't just run this for a few minutes and call it good. I had one throw a code 32. I changed the oil with 15w40 and it ran perfect for 3 hours. Then it dies with a code 32. 2 more oil chnages later, and won't run unless you hold the button. This generator is a POS.

If you fill the oil all the way to the top of the filler neck you overfilled it. If you had shown the oil dipstick after screwing it all the way in, it would have been clear that the oil level was way over the MAX mark. The correct level is somewhere at the bottom of the filling neck.

I have the Onan 6300, propane. Won't start, propane full, steps won't work unless I start the coach. Heart interface inverter panel is dead. Worked when I first bought it a few weeks ago. Plugged in at Quartzsite AZ RV park, so I guess not needed at the moment.

Thanks James! Using ethanol-free fuel (if you can find it) can help to avoid spoiling fuel and varnish build up in addition to running once a month under load. Love the great content! Even watched the annoying commercials to help with your RU-vid stats!

Watching you do this looks easy. But I am no mechanic. My problem is the generator runs great for all appliances until I turn the Air conditioner on then the generator just sputters out and dies. Any tips? Great video here and I have subscribed to your RU-vid channel to learn more and follow you. Thank you.

It looks the onan 5000 is better to work on. A man had a 2001 Winnebago that surge with uneven ''frequeny''.He could clean two more jets than the mainjet. And he told that the 1/4 knobs could be adjusted more by pulling it out with a srewdriver an turn some more. To get a bigger gap for the mainjet. It has worked for me on my Onan 4000W. Mine is a nightmare to work on, because the wires is too short and a real mess to get the controlboard back together in place. Greeting from Norway.

The 3rd Number 1 problem! Lol...I know what ya meant. Thanks for a great video!

On my class-C the generator is always having fuel problems and doing another carb swap currently. I'm seriously thinking about removing the generator and adding another larger inverter & charge controller and 2 more solar panels + 2 more LiFePo4 batteries and running the 120 vac off solar. My 2 current LifePo4 batteries have a 20 year warranty, same as my panels. Far longer than my new carb will last.. Thanks for the video..

I don't know if it is available out in your area, but an old company called Berryman makes B-12 that does a better job of cleaning and is a bit cheaper. Spray and liquid both work great.

Thank you for this video, my onan was surging, bought a new carb, followed your steps, swapped the old for new, generator started right up, no surge, running smoothly. Also put in the gas shut off valve, and ran it for an hour, then shut off the gas to the generator, let it run out, then parked it. Really appreciate you, thank you.

Before purchasing an expensive carburetor, try adjusting the altitude adjustment right under the fuel line. That's what it's there for. These engines are sensitive to both altitude and temperature variations. Oftentimes times a slight adjustment will cure the surge.

I've rebuilt hundreds of mower and motorcycle carbs. I'm pretty sure I'm trying that before spending 400 bucks on a new one.

Onan’s. Uff! They have always been crap. Been using then in phone vans since 1979. You never know when it will up and quit.

I hit the bell so I know when you put a video up. I can’t get enough.

Omg. $500 for a replacement carb is utterly insane. A tech could easily charge $1000 or more to do the job you just showed us. Spend the 5 minutes to drain the bowl if you're not planning to run the genny or before storing your rig, people. Great stuff James.

Thank you for the carburetor information. Listening to you, watching your facial grin now and then, being slender; You favor Clint Eastwood a good bit. Yeah, you do! 👍Have a great day.

James, this is the exact video I was needing! Our RV we bought must have sat for a while before they sold it to the dealer. It was running exactly like the one you showed. Hard to start and loped badly. I’ve run quite a bit of Sea foam through the RV and Generator from the tank. Now it runs much better after it starts, but is hard to start. In my mind, I can’t justify $500 for a replacement OEM carb. Just too hard to swallow that one. Thanks for the video! Respectfully, Kevin

I fixed mine the other day. Removed it,,, again ,,, from my camper and set it on my pistol range. Tested some 500 and 460 S&W hard cast. Onan died.

Thanks for your videos! This one has been super helpful. We do our own generator maintenance on the gas-powered micro-lite 4K on our 1995 Coachmen Santara QB280. Ran into an issue two weeks ago that still has us flummoxed. The U-shaped bracket for the air filter that is attached to the frame of the generator (to which the cap holding the filter screws) fell off. While the generator was running! What do we do to reattach it? Seems a bit beyond "bondo..." Tack weld it back into place? Anyone else had this happen?

Hey here a tip Permatex® High Tack® Spray-A-Gasket® Sealant, it will hold the gasket on making it easier.

Thanks very much for this video - I was able to replace my carb (and gas line) after being without a running generator for over a year. My model was exactly the same as the one in your video and there is probably no way I would have been able to do this job without watching your video a few times - Thanks! I have to say though, that I had a lot more trouble getting the gaskets in place and lined up in order to get the two bolts put in, but I eventually was able to get it put together and it's now purring like a kitten!! You are also correct when you say that these OEM carbs are VERY expensive...I live in British Columbia, Canada and the purchase price for the carb was $997.89 + tax (Canadian dollars), plus gaskets. Took a chance a bought it after viewing you video and thankfully it worked!

Disagree on the hz and voltage. Even a 30 AMP draw on 4K generator should not have more than 1 to 1.2 hz drag and 1-2 Volt drop. If you want to run any computer or electronics, ensure the frequency is NO HIGHER THAN 61.5 hz that typically puts the volts at 119. A large load will have 60 hz an 116-117 volts which is perfect. This is especially true if you plan to run a UPS for your laptops or TVs or anything like that. Most UPS will not click over line power if the frequency is over 1.5 hz above 60 or lower than 58 hz. My experience.

If you use startron every time you fill up and you will not have varnish build up. Never ever. I used stabil for years but seemed to have rubber breakdown issues. I have rebuilt or cleaned hundreds of carbs. Use Berryman carb cleaner, disassemble carb completely, blow all jet passages with high pressure air. In my life time I only found one carb on a high pressure washer that wouldn’t tune after a cleaning. Spraying carb cleaner on a dirty carb won’t always fix your problems. Weed eater type like Waldon, I get it. You can’t find kits like you use to.

Thank you. The best explanation and how to I have located.

Hey just wondering if you've heard of some of these not having the fuel drain screw that you were talking about my carburetor does not have that so I could not find anywhere to drain my gas from the carburetor and i'm frustrated

Welcome back. Another great video. Very informative, funny, thanks for the tip not to get the oil squirt at my face, thank you James. Happy trails!

Bought an older Weekend Warrior and didn't know how long it had been since genset had run but the carb was so badly caked with green slime and varnish I couldn't even pull the float needle out. Bought the amazon carb and it will start for just a bit and run like crap and flood motor so bad when you pull the plug gas drips out and the plug is full of gas. Pulled that cheap carb a few times to try and see of the float was sticking or something got behind the needle but i think its just a poorly made carb, now trying figure out if I should trust the guys the sell the "OEM" carb for $200??? Or just get the $400+ one. We don't even use a generator when we camp and have 600 watts of solar going.

My Onan 4000 (25 hours) doesn’t prime and the fuel pump makes no noise when priming. Once I get it started it runs fantastic. I’m thinking the pump is getting weak and the vibration of the running engine helps it to run. It will only click one time when priming. Anyone have this before?

Well done sir!! Loving the full length, step by step process on how to remedy this situation! Thank you

Well I found the problem on my daughters RV 4k Onan genset. The throttle plate shaft broke at the upper screw and the screw or something went through the motor. Anyone else experience this?

Well I'm a carpenter and a drummer. Not really good with mechanical stuff. I know I could take it all apart, getting it back together is another story. Lol ! That was a great demostration tho brother. Thank you for sharing. I fo have the same generator only it's in a tighter spot on my camper. Ugh

So I have an onan 4000 gensst no spark. I replaced the coil, module, rotor and circuit board. Still no spark. Turns over but no spark. I'm running.g out of hair to pull out do you have anything on that?? I'd really appreciate any kind of help. Thank you!

Just a question for you I have a 10.6 Bigfoot truck camper and ran my exhaust pipe all the way up past my roof a little bit and it has a slash at top to point the opening towards the back because I didn’t want to hear it or smell and it works great but a tiny bit of straight pipe sound and if my wife complains I may have to put a small muffler 3/4 the way up but I like the sounds it makes. When we get 3/4 of the way to where we are going to stop . I start the generator and AC to get it cooled down so when get inside it’s nice and cool inside and my 2500 Onan is run on propane and the only thing that happens is if is 2 table spoons of oil is just enough to let it start and motor slings oil all up in the motor and it will die. And it always happens when we are at a camp ground and some one will say how cool that is that my exhaust is above my roof and I tell them you can not point them straight up and blow soot water and tiny bit of gas and it will blow that stuff all over your camper and then somebody will ask me about their generator and 99 % of the time they are low on oil and I alway fill it at top oil full line and when they start their genset starts and stays running and then they say how much they spent at shops trying to fix it and the tec always says the same if that doesn’t do it you will have to find a Onan repair shop and the guy I bought it from then try to tell me they drained and fill it with synthetic oil and bugs all over the front of camper and I don’t think he did one thing right. He had duck tape on a crack on the cover for roof top ac and I camper lot that does alot of repairs and the parts gal me 90 bucks for cover and 90 shipping and the front happy Jack on drivers side was wrapped with duck tape because the manual socket would fall out. I got on Amazon AC was 90 bucks with free shipping and the happy Jack was a 15 cent C clip some people are so cheap and would not fix it or didn’t know how and both rear happy jacks was pulled lose from camper so I drilled the plate to the next size bigger lag bolts and I dipped the tip of each lag bolt wit a tiny bit West Marine and it is solid as a rock but if we go to Alaska I will take all four jacks of and roll them up in a piece of carpet,somebody doest hit them or me going threw a dip and there only 3-4 nuts to take them off and unplug the and screw cover back on. I seen a guy do that and said that’s a good ideal .

I had a 99 Brave with one of these 4000 quiet onan and it was brand new.After running for about 15 minutes it would start to surge and then die.It was closeing up the gap on spark plug.Open up gap and it would start rite back up.

Appreciate this video. I have a propane 3500 with starting problems and I think it’s the carb, but I’m getting too old for this DYI. It’s been difficult finding a generator mechanic, but thank you for pointing out the probable problems. From a happy 1996 Safari Trek owner.

Why does Onan use pipe threads on their oil drain plugs?

Hello, I have an older Kohler 4500watt. My start stop switch went bad so I removed it and left the wires disconnected and put in a key switch and now I don’t have any power from the generator. Does this need voltage for the exciter in order to have power!! It starts and runs great but no power. Thanks

My father had one that wouldn't stay running after sitting up for a few years. Tried cleaning the original one and could never find a rebuild kit. With no luck.. After seeing new prices and knowing he was going to sell it since he was about 85 at the time just put a knock off one on it. It ran fine for the few months he had it before it sold. After watching your video I would go with OEM for my personal toy hauler. Now I need to check the voltage and hertz after watching your video. Great video and content as always.

Any clue why my RV QG 400 would have oil on the air cleaner cover, control board, solenoid and battery cable? I did find a very small drip at the bottom of the head cover gasket right above the oil fill but the left side away from the engine is very oily. Thank you in advance

Surprised they do not have a crush washer on the drain plug, but using a little pipe dope is better than teflon tape getting in the oil, especially with no oil filter. Stay safe and healthy.

I have a 4000 lp onan... when I start it up it has a very ruff idle but does not surge.... it is ruff idle for about 3-5 mins and if I put a load on it it will run fine but ruff idle. After 3-5 mins it smooths out..... how do I fix it Thanks Chris

Same generator my problem was it started over revving, does this sound like something a bad carb could do??

On a Class A I have a question about starting the engine while hooked up to the pedestal. Is it ok to try and start the engine while connected? I ask because the batteries have died/drained and I am plugged in now trying/hoping they charge, but I'm a little worried about trying to start the ignition while plugged in.

I sure wish Oman would up date their stuff like smart throttle and fuel injection like Honda and it only adds gas to match the load and the number one thing that I tell people when camping ? Did you change your oil before this trip and they almost always say yes and I ask them does it start and die and I tell them your low on oil and my best advice is to fill your oil to the high mark and they fire right up .

I wonder if your going to store your motorhome for a couple months if you take the air cleaner off, fire it up. And spray WD40 into the carb then quickly turn the fuel off. Just a thought.

Excellent video! One noteworthy mention, is like 99% of the other videos I watched, no one mentions how they get past the problem with the choke and throttle butterflies closed at the same time so the carb will slip out. One RU-vid video I watched said they had to bend the tab on the choke linkage up so that it would clear the throttle linkage, thus enabling both choke and throttle butterflies to be closed (counterclockwise) and slip the old carb out and the new one in. Also, it would be helpful to know how you got the gaskets to line up for the bolts to pass through to secure the carb in place. I read in Cummin's service manual that we should not use gasket sealant to hold the gaskets in place. Besides, it's such a tight fit, I'm not sure that it would hold it on. I did find that pushing on the wall (side with air filter box), that created a slight bit of space to allow you to adjust the gaskets for proper fit, but even then, it's pure luck or Devine ntervention in my case, that allowed me to successfully get the carb installed and work first time without leaks. So again, if you could go back and add an addendum to your video on the subject of getting the carb out and new one in as it relates to those butterflies, that would be a huge help. I didn't like bending the tab on choke and then having to bend it back into place (making sure it was back to a 90 degree position so throttle would open and close like it should.

Will you come out to Mobile, Alabama and work on MY generator ? You look very confident and knowledgeable.

My generator is burning oil like crazy but no smoke. Pulled air filter off and it’s soaked with oil. What does that mean

I know the grounding wire for the carb solenoid has a screw that goes into the chassis, but I found it strange that you didn't place the lead behind the painted surface of the starter housing. other than that trial piece, I really appreciate your explanations on how to do things.

I need help not on generator, I have followed all your kiwee steps instructions but mine still I purchase a new part someone helped from rv place in Columbia he did wires now nothing they are bungee now.help

I am trying to find out how to adjust a float because in my generator which I have a I have a McGraw Edison on in 6.5 RV genset and I need to adjust the float in the carburetor and I need to know how to do it

OK I have a question for you. What happens if you got a code saying that it’s running at high RPMs how do you fix that?

Do you think I need to periodically run a propane generator?

I don't suppose you could take a look at mine It has been ridiculously hard to find help with my new to me motorhome and I am brand new and know nothing and feel like I have a target on my back getting pounded money Wise

@AZexpert if you use fuel shutoff till it dies, doest that throw an improper shutdown code that then makes it more difficult to restart?

The generator runs fine but the gen breaker keeps tripping. As soon as it's up to speed it trips. No codes. Can't find a short anywhere. Shore power is fine, with no issues. Suggestions?

Would a good carb cleaning fix this? Do I need to install a new carb? Is it so different from a motorcycle could I just clean out the jets?

I’ve broke fittings with Teflon tape , so I kinda stick with pipe dope.

25:18 100% agree. I've had two different Onan models now and both are a pain to fill. Getting the OEM installed oil filter off the newer one was 10x worse though.

That generator is the biggest head ache on my RV. Some folks on youTube claim that if you put more than the 1.5 liters of oil in, the generator will stop on hot days. I'm careful to measure out the oil. It's also 21 ft-lbs torque on the drain plug. Measure and you don't need to wonder if it will work. It's a shame they don't install generators with fuel injection and an inverter in these RV's. I may pull out this 175 lb monster and replace it with six solar panels and a bunch of LFE batteries. For the $4,000 they get for this generator, I could buy lots of panels and batteries.

This guy hit every snag I did. If he can do it you can do it. Thank you Sir.

Hey. My friend question how come a onan 4000 generator smoke white and won’t start

have same generator amazon got 2 of them first one was leaking not starting 2nd carb works great the onon factory carb took it a part they to rebuild it no it was no good any way have spare carb parts now

szeretnem tudni miert cserelte ki a mester a karburatort mi a hibaja miert fizet majd a megrendelo ??????????/

Stellar fix and replacement James! Appreciate the info and troubleshooting tips! Those carbs will varnish up quickly if infrequently used. Gotta run 'em or they will fail to run correctly or at all when you need them most. Always tricky steps getting those gaskets on right.

a leg egyszerubb es en lecsereltem az en munkam az ///jo ///nem javitunk mart csak cserelunk nemszukseges a gyakorlat sem truck vezeteshez sem mas javitashoz a bussines az megy a vevo ravanszorulva a szakertelem nelkuli emberekre hurrra hurra hurra oraber megy lejebb ///?=$

How much will it cost to ask you to fix the generator? Or who do you recommend?

When I bought my used rv and the onan had hardly ever been run -12 hours on it during 10 years(still actually started but surged badly)...lol......I did the seafoam injection directly to carb and it helped a little with the surging but it was the fuel pump that was the real culprit. It just wasnt delivering enough fuel...replaced and fixed. I would like to add that MANY people dont know about the elevation dial on the carb and that can make them surge and/or run bad. YES YES YES.....run them under load regularly and I always seafoam my fuel when I know Im not going to use my rv for a while...have used it all my life and it is excellent fuel stabilizer...AND also when Im not running my rv for extended period of time I try and get as much NON ETHANOL fuel in it as I can....call me over devoted!!! LOLLLLL

My 4000 generator run good but the exaust glowin red it’s normal

Great video 🎉 Can anyone tell me the fuel pump part number ? please 🙏 Thanks

Changed out carb and put in new fuel pump,no gas coming through line?

These generator shut off when outside temp is above 90 and main engine is running , any solution. It's a very common problem and there aren't any good solutions

You REALLY know your stuff! WELL DONE! ☺

Great detail! I was able to clean the carb with SeaFoam and other products. But it took a while. Now running it monthly has maintained function. Pushing the button once a month is easier than what you just viewed here.

Putting a starter in these is a pain you have to pull the whole generator out 😢

after watching the whole video. why get rid of the onan and replace it w/ a portable yamahas'.? the onan get so hot it is a wonder there is not more fires.

i'm pretty sure, the problem may have been caused by the cracked fuel line

Because I have the same generator on an Monaco monarch SE a 2005 with that same generator

I have a reminder on my Mac Calendar to cycle my genset once a month. I also if I can buy the ethanol free gas in either Oregon or Nevada I remember replacing carbs on my old genset it was easy to do, but, expensive. I think that I will follow Steve M's advice a put an inline fuel shut off on mine sounds like good idea!

Quick fix, use EFI. I guess I have been spoiled with all the marine generators that I have owned have been EFI based units both gas and diesel, from 5KW up to 32KW. Seem as compact and hard to get to as most marine units as well, especially when they put them in sound shield boxes. Great job sir. 🤠👍

My generator hasn't been run in years (long story short: my brother was borrowing the RV, got hurt, was in the hospital and now generally immobile). I'm flying to him so I can pick it up in a couple weeks. I live in Texas... I hope I can get it working or I'm sure to melt.

My solenoid just clicks is that my solenoid or is it my starter to that to the generator? going out

mitortenik ha eloszor leuriti a tankot teszteli a pumpat es igy tovabb csereli a hose csereli a nagy semmit amiert a megrendelo fizet nagyon sokat

what are the physical dimensions for the a 4000w onan generator. I'm considering removing the onan generator and replacing it with the guts of a champion inverter generator. I will need to add a modified remote switch and fuel pump. The onan is just not worth replacing once it's moved on to the next realm. The biggest problem with the Onan generators are that the diag codes are so obtuse that you have to fire up the parts cannon or disassemble the entire generator to work the problem when there is a simple issue like a code 32. Code 32 is when the crankshaft runs slow for 2 seconds. Causes: bad battery, bad battery connect, wrong oil viscosity, shot control board, or worn brushes on stator. Each time you try to work through one of these issues it's another $300 in parts. Screw that. It's time someone posts a guide on retrofitting a 15 years newer generator for $800 that fits into this space. First guy that makes a champion inverter kit to replace an onan 4000 wins the whole game. This is an old crappy design and it's way over priced. A 4000 Onan generator is $4000 new. Is the 4000 in the name referring to the watts it outputs or the fantasy price Cummings wants you to pay? I can get a more modern generator that should fit for $800 that is quieter and gets you out of that parts and support blackhole. Reality is Onan give you a lifetime warranty on parts, but their service partners jag you on service. Does that justify a $4000 price on a25 year old generator design? Yeah that generator with various "specs" has been manufactured since the mid 90's. WTF? I don't think so. If someone want to talk about making a modern plugin replacement for this generator that's sub $1000, feel free to hmu.

Super glue is your friend with these gaskets makes life happy

Thank you for an update excellent video. I’ve had a number of carbs replaced over the last 25 years. After your video, I might try it myself next and if it happens again. I drain the fuel now. ( Learned the hard way this must get done). Great information. Thank you

Some s0b ripped off the control board on my kids side RV. I found one and it runs bad. Interesting

mennyit futott a generator a szerviz elott ha nem megy a generator nem szennyezodik a szuro

No truer words have been spoken...."whatever you do dont hit the switch with the oil cap off, it will splash you in the face" yep...been there.

can you convert a Cummins 6500 prophane to gas