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Author Topic: Carb on Onan 4000 - to be replaced  (Read 8730 times)

snasis

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Carb on Onan 4000 - to be replaced
« on: June 06, 2011, 11:17:53 AM »
Hello all,

I have just been told by the RV sevice place that my carb on the generator needs to be replaced again from last year because it sat too long and the fuel gummed up the jets.  He recommends that we run the generator once a month to keep this from happing.  Any thoughts or suggestions.

Thank you in advance,

Sean

Molaker

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Re: Carb on Onan 4000 - to be replaced
« Reply #1 on: June 06, 2011, 11:20:21 AM »
A carb replacement would be pretty expensive.  Have they even tried cleaning it?  If not, maybe you want to find someone who will.
Tom & Joyce and Ditto the "don't tell her she's a dog" Westie
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JayT

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Re: Carb on Onan 4000 - to be replaced
« Reply #2 on: June 06, 2011, 11:46:03 AM »
This also happened to me and after some research I discovered the following. Gas turns to a resin inside the carb and clogs up the float needle and jets. Onans recommendation is to purchase a rebuild kit for $80+. My recommendation is to pull the carb (very easy to do) then spray/flood the carb with carb cleaner (making sure you fill the bowl) and let sit for about two hours then shake out and do again then shake out again and re-install.

I hope this helps, good luck

Jay T
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Water Dog

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Re: Carb on Onan 4000 - to be replaced
« Reply #3 on: June 06, 2011, 11:57:06 AM »
Not only should a generator be run every month, but it should be run for a minmum of about a half hour per month under load. Other than running fresh gas through the carb, this also helps keep the slip rings in the gerator clean, and some lubrication going in the engine. Generators are built to be ran, and like many other mechanical things will deteriorate over time if just left sitting.
Dennis

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Gary RV Roamer

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Re: Carb on Onan 4000 - to be replaced
« Reply #4 on: June 07, 2011, 11:59:48 AM »
Running the genset periodically is cheaper and less frustrating than continually rebuilding or replacing carbs.
Gary
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2004 American Tradition
2007 GMC Acadia
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TOMAX

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Re: Carb on Onan 4000 - to be replaced
« Reply #5 on: June 07, 2011, 12:12:24 PM »
My gen sat for 10 years. It would fire and almost run. I cleaned mine by mixing injection cleaner and a small amount of gas, I discounted the fuel line hose at the filter and stuck into the mixed gas. I would turn it over a bit to draw in some of the mixture then let it set. Did this a couple of times a day, after 2 days it would start and run on the mixture. Hooked up the fuel line and worked fine.
Tom
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Paul & Ann

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Re: Carb on Onan 4000 - to be replaced
« Reply #6 on: June 07, 2011, 12:25:20 PM »
Hello all,

I have just been told by the RV sevice place that my carb on the generator needs to be replaced again from last year because it sat too long and the fuel gummed up the jets.  He recommends that we run the generator once a month to keep this from happing.  Any thoughts or suggestions.

Thank you in advance,

Sean

Sounds to me like this guy is trying to stiff you.  He did it last year, and he is thinking you will fall for it again.  First of all, I believe that there is only one jet, and all you have to do is as other suggest use some carb cleaner on it.

I agree with others it is a good idea to run your generator monthly.

If you run ethanol blended gasoline in your generator, the ethanol in the gas will keep you carbureator clean.

Best of luck.

Paul

catblaster

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Re: Carb on Onan 4000 - to be replaced
« Reply #7 on: June 07, 2011, 03:52:04 PM »
Touchy subject ethanol...it will not keep your carb clean, in fact it is corrosive to certain aluminum alloys and steel parts in the carb. Ethanol undergoes phase separation with as little as 1% moisture and turns into a destructive agent to a lot of rubber parts, ie diaphragms in 2 stroke motors.
Will and Jane
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skyking4ar2

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Re: Carb on Onan 4000 - to be replaced
« Reply #8 on: June 07, 2011, 04:01:53 PM »
Touchy subject ethanol...it will not keep your carb clean, in fact it is corrosive to certain aluminum alloys and steel parts in the carb. Ethanol undergoes phase separation with as little as 1% moisture and turns into a destructive agent to a lot of rubber parts, ie diaphragms in 2 stroke motors.

That's why we don't burn ethanol added automotive fuel in airplanes, even though we can have a supplemental type certificate that burns non-ethanol automotive gas.  8) When in doubt, throw it out!
Kim & Christi Bertram
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Paul & Ann

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Re: Carb on Onan 4000 - to be replaced
« Reply #9 on: June 07, 2011, 04:09:37 PM »
Touchy subject ethanol...it will not keep your carb clean, in fact it is corrosive to certain aluminum alloys and steel parts in the carb. Ethanol undergoes phase separation with as little as 1% moisture and turns into a destructive agent to a lot of rubber parts, ie diaphragms in 2 stroke motors.

 I have heard about phase separation, but have never seen it in 30 some years of using ethanol blended gasoline.  I dont believe that Onan generators are 2 stroke motors, so that doesnt apply.  Generator repair places love people who dont like ethanol.  A new carburetor every year sounds like a good plan, for then. :)

Paul
 

skyking4ar2

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Re: Carb on Onan 4000 - to be replaced
« Reply #10 on: June 07, 2011, 05:28:21 PM »
Paul,

I don't think we are talking about just two stroke engines here.

http://www.aopa.org/whatsnew/region/2007/071129or.html

The damage to seals and rubber parts is well documented and when engines are run on a regular basis, the other corrosion issues are not as prevalent. For generators, and some airplanes, often used more occasionally than daily, there is a toll.

I have never heard a carburetor guy talk nice about leaving old fuel in any kind of carburetor, and especially not fuel with ethanol. I won't even leave "car gas" in the plane, which has a supplemental type certificate for auto fuel,  for any length of time (a month) before I mix it with avgas or fly it out.

That's a personal solution and your mileage may vary.  8)
Kim & Christi Bertram
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Paul & Ann

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Re: Carb on Onan 4000 - to be replaced
« Reply #11 on: June 07, 2011, 05:45:04 PM »
Paul,

I don't think we are talking about just two stroke engines here.

http://www.aopa.org/whatsnew/region/2007/071129or.html

The damage to seals and rubber parts is well documented and when engines are run on a regular basis, the other corrosion issues are not as prevalent. For generators, and some airplanes, often used more occasionally than daily, there is a toll.

I have never heard a carburetor guy talk nice about leaving old fuel in any kind of carburetor, and especially not fuel with ethanol. I won't even leave "car gas" in the plane, which has a supplemental type certificate for auto fuel,  for any length of time (a month) before I mix it with avgas or fly it out.

That's a personal solution and your mileage may vary.  8)

For the record the OP was talking about an Onan generator, not a chainsaw, or an airplane.  I have no experience with ethanol with either of these types of motors.  I do have lots of experience with ethanol blended gasoline in cars, pickups, and motorhomes going back 30 plus years.  I have never had a problem with a fuel system in a vehicle that I have owned from using ethanol blended fuels, with the exception of having to change fuel filters a couple of times in vehicles that had not had ethanol blended fuels in them previous to my buying them.  I currently have a 1997 Chevy S-10 Blazer that has 190,000 miles on it, and it has had ethanol blended fuel in it since it was new, and the only problem with the fuel system I have had with it is that about at 170,000 miles I had to replace the fuel pump. I dont think that is too bad a record.

There are lot of scare tactics, misinformation, and just lack of knowledge on the issue of ethanol.

Everyone is free to believe and act as they wish, I am just trying to provide some real life experience.

Paul

gwcowgill

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Re: Carb on Onan 4000 - to be replaced
« Reply #12 on: June 07, 2011, 07:03:20 PM »
Clean the carb on the Onan using carb cleaner or even Fuel Injection cleaner as suggested above and you should be fine. Have done i numerous times on different Onan gensets with great success. Don't let them sell you a new carb. Remember the carb is still good just gummed up.
2009 Bounder 36B, 2014 Honda CR-V, various grandchildren when school is out. KG4LHS

tvman44

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Re: Carb on Onan 4000 - to be replaced
« Reply #13 on: June 07, 2011, 07:07:57 PM »
After getting it clean put Sta-bil in the gas to slow down the break down.

catblaster

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Re: Carb on Onan 4000 - to be replaced
« Reply #14 on: June 07, 2011, 07:33:46 PM »
2 cycle engine was used as an example where ethanol destroys membranes. I realize Onan generators are not 2 stroke engines, I have 3 here and grateful 1 is diesel. I also have a garage full of ethanol ruined motors, 2 strokes and small 4 stroke motor are more susceptible because of their smaller passageways. In Florida where I am the humidity is high and some dealers have a hard time keeping up with moisture. I have gotten cans of fuel home just to have them begin separation in a week.  There was an article that claimed ethanol was more stable at higher concentrations such as 15%. Bottom line is run the machine regularly and if possible run the motor until the carb runs dry of fuel. It probably is easier and more profitable for a generator shop to replace than to repair and they cant be blamed for a crappy rebuild.
Will and Jane
95 Winnebago Luxor

Paul & Ann

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Re: Carb on Onan 4000 - to be replaced
« Reply #15 on: June 07, 2011, 07:49:35 PM »
2 cycle engine was used as an example where ethanol destroys membranes. I realize Onan generators are not 2 stroke engines, I have 3 here and grateful 1 is diesel. I also have a garage full of ethanol ruined motors, 2 strokes and small 4 stroke motor are more susceptible because of their smaller passageways. In Florida where I am the humidity is high and some dealers have a hard time keeping up with moisture. I have gotten cans of fuel home just to have them begin separation in a week.  There was an article that claimed ethanol was more stable at higher concentrations such as 15%. Bottom line is run the machine regularly and if possible run the motor until the carb runs dry of fuel. It probably is easier and more profitable for a generator shop to replace than to repair and they cant be blamed for a crappy rebuild.

I am not sure what they are selling you in Florida, but here in Iowa, I have never seen separation in ethanol blended gasoline.
As I said in another post on the topic of ethanol, I buy ethanol blended gasoline to run in my 14.5 HP four stroke engine on my lawn mower six gallons at a time.  More than once this amount  has lasted me more than a year, but still no separation, and no problems with my lawn mower engine.  Maybe I am just lucky.

Paul

snasis

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Re: Carb on Onan 4000 - to be replaced
« Reply #16 on: June 08, 2011, 02:09:28 PM »
thank you all for your insight and help!

Sean

gwcowgill

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Re: Carb on Onan 4000 - to be replaced
« Reply #17 on: June 08, 2011, 09:19:56 PM »
Ethanol is alcohol which absorbs water. In high humidity climates water will be absorbed into an open to atmoshere fuel storage system. All new vehicles must have a closed system however, what about where you get your fuel. Take a fuel sample, shake it up in a glass container and then let it set for abouty 10 minutes and then see how much water is in your fuel. You may be surprised if you are using ethanol based fuels from unreliable sources.
2009 Bounder 36B, 2014 Honda CR-V, various grandchildren when school is out. KG4LHS

Paul & Ann

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Re: Carb on Onan 4000 - to be replaced
« Reply #18 on: June 08, 2011, 10:54:14 PM »
Ethanol is alcohol which absorbs water. In high humidity climates water will be absorbed into an open to atmoshere fuel storage system. All new vehicles must have a closed system however, what about where you get your fuel. Take a fuel sample, shake it up in a glass container and then let it set for abouty 10 minutes and then see how much water is in your fuel. You may be surprised if you are using ethanol based fuels from unreliable sources.

Some states like Nebraska do not monitor the ethanol content in the fuel that is sold, or the octane of the fuel sold.  In Nebraska all they check is for the accuracy of the pump, so they dont care what it is that is being sold, as long as you get a gallon when you pay for a gallon.

In Iowa they check not only for accuracy of the pump, but what it is that you are buying.  Maybe one reason so many people have problems with ethanol blended fuels is that other states are like Nebraska, and not Iowa.

Paul

gwcowgill

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Re: Carb on Onan 4000 - to be replaced
« Reply #19 on: June 09, 2011, 06:27:15 AM »
I am not sure that the actual content of ethanol is important as much as how the ethanol based fuel is stored and what conditions it is stored under, On the other hand, alcohol burns slower than gas which does cause some loss of power which the newer cars compensate for by higher compression ratios. Those running 80's technology need to be leery of ethanol based fuels.
2009 Bounder 36B, 2014 Honda CR-V, various grandchildren when school is out. KG4LHS

Gary RV Roamer

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Re: Carb on Onan 4000 - to be replaced
« Reply #20 on: June 09, 2011, 08:45:08 AM »
Ethanol is indeed a touchy subject - it seems that most everybody has a theory about how terrible it is, based on some fact that may or may not be relevant to engine operation.

What IS a well-established fact is that gasoline (whether ethanol or not) that sits in a carburetor for weeks or months will slowly evaporate and leave a residue that clogs the tiny passages in a carb. Sometimes a shot of carb cleaner is sufficient to clean it out, but more often it requires removal and dissassembly and a thorough soaking/cleaning. That is time consuming and expensive at todays shop labor rates, and still may not be successful if something was damaged or the solvent did not do its magic the first time. For that reason, most techs would rather replace the carb and know it will work, avoiding a dissatisfied customer and a "do over" repair they probably cannot charge for. For that reason, carb cleaning and rebuild is a disappearing service, done mostly in back yards and country shops.  I've become rather expert in removing and cleaning the twin carbs on the outboard engine of my bass boat, which doesn't get used very much.
Gary
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zmotorsports

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Re: Carb on Onan 4000 - to be replaced
« Reply #21 on: June 09, 2011, 10:21:58 AM »
I agree with Gary that many shops will not even touch a carburetor any more, whether on a car or generator.  If they mess with them at all they R&R (remove & replace) only.

You could pull the carb off and clean with solvent to see if the circuits can be cleaned.  Usually the idle circuit is the first to suffer symptoms due to its size being much smaller than the main metering circuit.  Fuel residue is usually the culprit of these blockages.

One thing I would recommend after either yourself cleaning the carb or even a shop if you are not 100% sure of their abilities is to plug a voltmeter into a recepticle when you get it back running prior to turning on any electrical equipment.  I have seem too many audio/video components and electrical devices get damaged from someone not knowing what they are doing with a generator carburetor.  Generators need to be set to voltage and frequency not RPM like most other small engines.

I generally set the carburetor to produce about 125-128 volts and approx. 62-63 Hertz under a no load condition.  When you apply load it will pull the voltage and frequency down somewhat and usually right on the money, about 120-123 volts and 60 Hertz.

Mike.
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Macrosill

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Re: Carb on Onan 4000 - to be replaced
« Reply #22 on: June 11, 2011, 08:06:18 AM »
Hello all,

I have just been told by the RV sevice place that my carb on the generator needs to be replaced again from last year because it sat too long and the fuel gummed up the jets.  He recommends that we run the generator once a month to keep this from happing.  Any thoughts or suggestions.

Thank you in advance,

Sean

Try running the genny with some fresh gas and Seafoam additive.  I used it on my genny a couple weeks ago and it worked great.  The genny had sat for 2 years with the previous owner.  It would have a hard time starting but would eventually start, idle rough and not be able to keep running under a load.  I bought some fuel line, placed some fresh gas in a 2 gallon gas can and ran the fuel line from the fuel filter to the gas can.  After running for about 30 minutes the idle smoothed out and after a few hours running for a couple days she runs fine under a load from the A/C. 
Thanks,
Brian

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TV = 2003 Chevrolet Suburban

grayboy

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Re: Carb on Onan 4000 - to be replaced
« Reply #23 on: June 15, 2013, 12:55:16 PM »
I HAD THE SAME PROBLEM WITH MY GENERAC GENERATOR 6500 WATT. THE RV OUTFIT TOLD ME THEY DON'T REBUILT CARBURATORS BECAUSE THEY CAN'T BE TOTALLY REBUILT. HIS PRICE WAS $600 TO REPLACE. I SPENT MANY HOURS ON LINE TRYING TO FIND MY JAPANEESE NIKKI CARBURATOR WITH NO RESULTS. I FINALLY E-MAIL CHINO MOWER IN CHINO, CA. THEY HAD A REPLACEMENT FOR $143 AND WOULD TAKE 2 WEEKS TO GET IT. I TOOK THE OLD CARB AND SOLINOID IN TO MAKE SURE IT WAS THE RIGHT ONE. WHILE THERE THE OWNERS SON TOOK THE SOLINIOD OFF AND FOUND IT WAS STUCK, HE MESSED WITH IT FOR ABOUT 5 MINUTES AND GAVE IT BACK TO BE AND SAID, BEFORE YOU BUY A NEW CARB, PUT IT BACK ON AND SEE IF IT WORKS NOW. I REINSTALLED THE CARB IN 5 MINUTES AND THE GENERATOR RUNS GREAT NOW. I ALSO CLEANED IT BY SQUIRTING CARB CLEANER THRU EVERY HOLE I COULD FIND, SOME AT MY AGE ARE HARD TO SEE, SO IF YOU HAVE A YOUNG SON OR FRIEND HELP YOU IT MIGHT HELP. SO ANYWAYS, INSTEAD OF $600, IT COST ME $18 FOR MOWER SERVICE TO MY RV GENERATOR .

JEB "GRAYBOY"