Carb on Onan 4000 - to be replaced

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snasis

New member
Joined
Jul 15, 2010
Posts
3
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
 
A carb replacement would be pretty expensive.  Have they even tried cleaning it?  If not, maybe you want to find someone who will.
 
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
 
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.
 
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.
 
snasis said:
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
 
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.
 
catblaster said:
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!
 
catblaster said:
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
 
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)
 
skyking4ar2 said:
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
 
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.
 
After getting it clean put Sta-bil in the gas to slow down the break down.
 
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.
 
catblaster said:
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
 
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.
 
gwcowgill said:
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
 
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.
 
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