A little OT, Onan P224G-I on a sawmill won't idle.

[obsolete]

I have an Onan P224G-I engine, spec, 10842C, on a Woodmizer mill that will not stay running at idle without partial choke, at full speed it works fine.
It is not the original engine, a pretty low hour replacement in otherwise good condition.
Is anyone familiar with this engine? I have the service manual and have gone through all the carb and governor settings and adjustments, moving the idle jet screw does not change anything.
Seems like the idle jet is clogged.
Is the jet removeable on these carbs? are they easily rebuildable? Advise?
Thanks.

 

[ianjoub]

Not familiar with this particular engine, but:

1. Remove the air cleaner, start it, rev it up to full song, cover the air intake with your hand. All that vacuum may pull a small obstruction through a clogged jet.

2. Can you do a leak down test? Tight valves can do this as well.

 

[Delmer]

Sounds good to me. Before you mess with the carb though, check for vacuum leaks, spray the gaskets with penetrating oil or even water, check the intake manifold bolts are tight. Change the spark plugs, just for fun. Then dig into the carburetor, sometimes they're easy to fix, sometimes it doesn't do anything, but a new one works.

 

[willie59]

9 times out of 10, a small engine that won't idle unless the choke is partially pulled is a carburetor that's suffering from ethanol poisoning, that crap will destroy a carb on a small engine. And when I've found one suffering from that I've never found a reliable way to bring it back to life, instead replace the carb. And if and when you do get it sorted out, either run the bowl dry of fuel when you shut it down or use an ethanol stabilizer. In my area I can still get 100% gasoline, that's all I use in small engines, I never use ethanol fuel.

 

[Welder Dave]

Small engines have very small orifices in the carb. and jets that only take the tiniest bit of dirt to clog. The carb. can be disassembled and the jets and other parts can be cleaned out. A very fine wire or even a tip cleaner for a cutting torch can be used to clean jets. You could try blowing compressed air through the carb. but just a quick blast. First thing I'd do though is take the float bowl off and see if there's dirt, sediment or discoloration in the fuel. Not sure on your particular carb. if there is a jet accessed once the float bowl is off. Would be best to get an exploded view of the carb. to show all the small parts.

 

[Tinkerer]

The plug over the idle fuel limiter has to be removed to get access to it.

 

[Zewnten]

9 times out of 10, a small engine that won't idle unless the choke is partially pulled is a carburetor that's suffering from ethanol poisoning, that crap will destroy a carb on a small engine. And when I've found one suffering from that I've never found a reliable way to bring it back to life, instead replace the carb. And if and when you do get it sorted out, either run the bowl dry of fuel when you shut it down or use an ethanol stabilizer. In my area I can still get 100% gasoline, that's all I use in small engines, I never use ethanol fuel.

Small engines have very small orifices in the carb. and jets that only take the tiniest bit of dirt to clog. The carb. can be disassembled and the jets and other parts can be cleaned out. A very fine wire or even a tip cleaner for a cutting torch can be used to clean jets. You could try blowing compressed air through the carb. but just a quick blast. First thing I'd do though is take the float bowl off and see if there's dirt, sediment or discoloration in the fuel. Not sure on your particular carb. if there is a jet accessed once the float bowl is off. Would be best to get an exploded view of the carb. to show all the small parts.

So ethanol is rotten after 3 months, and it will varnish your carb. Clog or restrict all the little holes @Welder Dave mentions. The only thing I've found is if you can find a gasket kit drop it into a sonic cleaner with simple green and rebuild it sometimes it work or if you can't put a cap full of varnish cleaner in the bowl and give it a couple minutes. Make sure you only run non-ethanol if you're going to let fuel sit.

 

[willie59]

So ethanol is rotten after 3 months, and it will varnish your carb. Clog or restrict all the little holes @Welder Dave mentions. The only thing I've found is if you can find a gasket kit drop it into a sonic cleaner with simple green and rebuild it sometimes it work or if you can't put a cap full of varnish cleaner in the bowl and give it a couple minutes. Make sure you only run non-ethanol if you're going to let fuel sit.

To be clear, I'm not an expert on this, nor do I claim to know exactly, as far as the chemistry goes, what is happening. But my layman observations, both 100% gasoline and ethanol gas will become "rotten" over time. 100% gasoline will cause varnish. But I think, at least I've observed, ethanol does something different, even worse than varnish in my opinion. Again, I don't know what it is, my theory is the sugar in ethanol. It makes a residue in carburetors that I have yet to find a solvent that will dissolve it. Maybe there's something out there that will, I just haven't found it. But that's the stuff that will kill a carb, clogs those tiny passages that fuel is metered through, especially at idle. Since I've never found a good/reliable solution, that's why I only use 100% gas. And for winter storage I use StaBil fuel stabilizer. Been doing this for years in my mowers, blowers and weed whackers. Come spring, they all light up and run with no issues.

 

[Welder Dave]

Some mechanics recommend using premium gas with the highest octane numbers. Have also heard ethanol eats rubber hoses. Maybe little bits of deteriorated hose have plugged the jets. Sometimes just dirty fuel will do it and not methanol related at all.

 

[Delmer]

Ethanol sucks water out of the air, the water mix corrodes aluminum bad. That aluminum corrosion plugs stuff. Best I can tell.

 

[Welder Dave]

There's a reason they make small cans of pre-mix and small engine gas you buy in stores rather than at the pump. It doesn't contain ethanol. It's expensive but can save having numeric issues.

 

[obsolete]

I do run the carb dry on this and all my gas engines that are not used all the time, I have a bunch of old Cat diesel tractors that are all pony start, running the pony dry every time they are used instead of using the shut off switch is proper procedure and a habit I got into long ago.
Looks like if I pull the top off the carb I can get to the idle jet, will be able to see if the bowl is corroded and full of junk.

 

[ianjoub]

2 stroke oil seems to help as well, yes, even in 4 stroke engines. When the gas evaporates, the oil residue is left behind. When new fuel is introduced, the oil helps everything to flush through.

 

[MarshallPowerGen]

As others have already said, get in those jets with a welding tip cleaner and get them cleaned out.

Look into a kit for that carb before tearing too far in, I remember having to make one of those lid gaskets in the picture last time I was in one of those for one reason or another. I think I recently threw out the template after 10ish years of it sitting in a folder.

 

[ianjoub]

I have some of these. They are sized for various jets.

https://www.amazon.com/Carburetor-Cleaner-Cleaning-Motorcycle-Chainsaw/dp/B07Q56HGHX?th=1

 

[mekanik]

Try not to enlarge the jets cleaning them. Its easy to do. I use piano wire to clean jets its stiff and works well. If the jets are really small guitar strings will work. I was at the local music store buying some guitar strings and told the sales person what I wanted them for.
He told me I was not the first person he sold guitar string to for cleaning carb jets.

 

[obsolete]

Success !

I decided to go into the carb and see how it looked, here is what I found and did.
The top came off the carb without tearing up the gasket, the Idle jet comes out once the top is off, and there was a chunk of green crud completely blocking that jet, my torch tip cleaning tools were perfect to do the job, and of note, the actual orifice is a little way up inside the idle jet tube, not right at the tip, good thing I was being very careful in cleaning and inspecting it, it would be easy to just ream it out to the tip hole size.
It was in good shape and pretty clean other than that one little chunk of crud, went back together ok and runs like it should.
Thanks for all the advise, tips and encouragement.

 

[randy448]

The plug over the idle fuel limiter has to be removed to get access to it.
View attachment 283482

Hex bolt on lower right in picture gives access to main jet. Allen wrench hole to remove if I remember correctly. Careful not to drop it! Clean with torch tip cleaner.