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Onan generator

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Tarnold

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Onan generator
« on: July 31, 2023, 06:03:04 pm »
Just cleaned a rats nest off top of subject.  While there tried to check condition of air filter.  Ok, take off wing nut, remove outer cover, then what.  The threaded shaft that holds the wing nut is too long to allow the filter to slip off.  Turned that thing every which-a-way to get it to slip out. Nope. Other than bending the rod(nope) what do you do?

Also generator slows down a little(turned  a/c off) backfires and then revs back up, runs 5 min then repeats.  Haven’t run it in a while, I know, can hear the transfer switch hammering on and off when it does.  Hope some more running might clean it out.  Not in the mood to attack the fuel filter in this heat.  Been parked for several months with only occasional running
Terry

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Joseph

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Re: Onan generator
« Reply #1 on: July 31, 2023, 07:04:41 pm »
The air filter has to be at a particular angle to remove or reinstall.  Take a look at the utube videos and you’ll see the right angle.  As far as the backfire, that’s a tough one.  Could be your carb is dusted from letting it sit with ethanol gas in it.  There three ways to attempt to clean it up.
One , run a gravity feed to the carb and use half gallon of gas and several ounces of sea foam.  Second option is to add several cans of sea foam to your main tank.  At least 3 ounces for every gallon.   Last would be to change out the carb itself and then add either a fuel valve or a fuel pump switch to shut down the fuel supply so this doesn’t happen again.   Adding the fuel stop , either style is important no matter if you replace or get the current carb cleaned.

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Tarnold

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Re: Onan generator
« Reply #2 on: July 31, 2023, 07:40:57 pm »
Ok, watched the YouTube, so not just me. Will try again.  Did notice though that the vid showed an inner and outer wing nut.  I only have the outer??

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Tarnold

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Re: Onan generator
« Reply #3 on: July 31, 2023, 08:09:46 pm »
Also regarding seafoam.  Some times it works too good.  Dumped a can in my last RV, and drove about 30 miles and the check engine light came on.  My scanguage told me bad o2 sensor.  Guess it broke something loose and clogged the sensor.

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mikeh

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Re: Onan generator
« Reply #4 on: July 31, 2023, 08:44:10 pm »
Terry,
Just changed my genny air filter out last week on my 2019 2552 (along with an oil change).  Joseph is right.  It's really tricky to get the filter out--I could only get it out and back in one particular way--but it did go.
As far as I know, you should have TWO wing nuts on the threaded shaft--one clamps the air filter tightly in the housing, and one holds the outer cover in place.  Although the very old Onan generators had a different air cleaner cover, I think that two-wing nut arrangement goes back at least until 2006 or before that.

In addition to Joseph's advice on your backfire and erratic running issue, another solution is to clean the carburetor bowl and main jet.  On two occasions, when I let my generator sit too long without exercise with E-10 fuel in the system, I had to drop the carb bowl and clean it out.  I found greenish gas and deposits in the bowl bottom and main jet area.  After cleaning everything up and flushing fresh fuel through it, it solved the issue both times.  Based on my experience, I suspect your problem is in the carburetor bowl instead of the fuel filter.
For the past two years I've added Stabil to the E-10 before winter storage, and been more careful to run that generator every month or two.  That has prevented recurrence of the problem.
Mike

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Joseph

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Re: Onan generator
« Reply #5 on: August 01, 2023, 10:04:11 am »
Terry. Your concern about a sensor would push me to use a gravity feed.    As Mike said you can attempt to clean the carb. They really aren’t designed to be taken apart and cleaned but your not out anything to try.   The ethanol gas when it dries up leaves a chalky film.   The jet is so small it’s really hard to clean well even soaking.  I replaced a carb with a knock off and it was great for a couple years.  I got cancer and fell behind in running it frequently and it was toast.  I replaced and a few hours of use later my fuel pump went bad as well.  I replaced and relocated the fuel pump and added a toggle to pumps power lead so now I run it dry after every use.  ( relocated because it’s a bit of a job to get to and in a hot location that many believe causes failure to pump as it over heats). Btw.  After relocating I could change the pump out in under 15 minutes.

One thing to note should you install a after market carb.  On this recent install it ran way too rich.  Even adjusting the little black control to 6,000 ft ( I live 15’ above sea level).  I popped off that black knob and leaned it all the way out.  Then opened a full turn and ran for a bit and checked the plug and adjusted from there.   Only took a couple runs and it was dialed in.

And Mike is correct . There are two wing nuts.

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WillLloyd

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Re: Onan generator
« Reply #6 on: August 02, 2023, 07:45:46 am »
When I winterize the generator, I disconnect the fuel line from the main tank at the generator. Add a temporary fuel line and dip it in a bottle of stabilized fuel. Then I run that through everything, turn it off, put it back together, and don’t touch it till spring. So far, after many years, I have not had generator fuel related problems.

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NCPinz

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Re: Onan generator
« Reply #7 on: August 02, 2023, 03:50:31 pm »
When I winterize the generator, I disconnect the fuel line from the main tank at the generator. Add a temporary fuel line and dip it in a bottle of stabilized fuel. Then I run that through everything, turn it off, put it back together, and don’t touch it till spring. So far, after many years, I have not had generator fuel related problems.

Great advice.  That will be added to my winterizing list.

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Joseph

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Re: Onan generator
« Reply #8 on: August 02, 2023, 06:25:54 pm »
Will I guess we both use a similar method.   I add stabilizer to my main tank. Having a switch on the fuel pump allows me run it dry and still allows for exercising  the gen every every 5-7 weeks and then run it dry.  I know a lot of people don’t exercise their gen as suggested and never had a issue, myself included. I only changed to running it because Ca gas is garbage. Doesn’t look or smell like gas I get once I leave the state.

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WillLloyd

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Re: Onan generator
« Reply #9 on: August 03, 2023, 06:50:13 am »
Good point, as mentioned by Joseph, I do run it dry after I put the stabilized fuel through the generator system. Just pull the temporary hose out of the bottle and let it run till it stops.

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mikeh

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Re: Onan generator
« Reply #10 on: August 03, 2023, 10:08:46 am »
Since I don't use my RV over the winter months, my process for storage for the past couple years has been to fill the fuel tank completely, add stabilizer, and run both the Ford and generator engine enough to ensure the stabilized gas is through the system.  I then fire the Ford and generator engine for an hour or so every month or 45 days until used again.  That's worked well.
My generator was one of the first (in early 2019) to have a fuel shut-off valve installed in the genny fuel line as standard by Phoenix (or so they told me).  I haven't used it to run my generator dry each time, but I do think that can be a useful help given the design of the Onan carburetor.

I've done a lot of small-engine work, and have repaired/rebuilt/replaced numerous carburetors used on Briggs, Tecumseh, Kohler, Kawasaki, and other engines.  Using the "run-dry" approach for storage on most of them won't hurt, but is not really a totally effective approach. The Onan carburetor has a unique design that I think is what makes it so sensitive to fuel problems with stagnant fuel--as well as allowing the "run-dry" approach work on the Onan.  Most bowl-type carburetors have the main jet and actual fuel pick-up point in the fuel bowl located some distance above the bowl bottom.  That means that whenever you "run those carbs dry", there is still residual fuel in the bottom of the bowl that remains to go bad since you don't actually get all the fuel out of the bowl.  That also means, though, that they're not as subject to problems from tiny bits of contamination on the very bottom of the bowl.  If you will look at your Onan carburetor, however, you will see that the main jet and adjustment needle is a horizontal affair located in the absolute bottom of the fuel bowl.  It essentially pulls fuel off the very bottom of the bowl.  That means that ANY deteriorated fuel or residue at the very bottom restricts the jet and fuel pick-up--so the Onan is highly sensitive to any type of poor fuel and pretty easily can give fuel problems.  Conversely, however, when you run an Onan carb dry, you're pretty much getting all the fuel out of the bowl, so it's more likely to be a successful technique with the Onan than with many other engines.

By whatever method (stabilizer, running, run-dry, etc) you especially need to prevent fuel deterioration (especially with E-10) in the Onan carb.

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Joseph

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Re: Onan generator
« Reply #11 on: August 04, 2023, 12:40:40 am »
On my after market carb after running dry I open the drain valve at the bottom of the bowl as well.   Sometimes I get a few drops other times nothing. 

I avoided the fuel line valve approach.  Too many reviews of them leaking over time.