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Lt40 Help!! Onan 24 will only run full choke.

Started by Peder McElroy, August 07, 2012, 12:41:29 AM

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Peder McElroy

My onan 24 will start and run for awhile at 1/2 choke and then die unless I put in full choke.It just started to do this,think it would be fuel??? Battery is full charged and fuel is new.Any ideas would sure help.
Thanks
Peder

logboy

Time to clean the carb. Might as well check/replace the fuel filter while you're at it, and replace any old fuel lines that look cracked or corroded as well. Your local small engine repair or auto parts store should have a carb rebuild kit if necessary.
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losttheplot

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Cutting Edge

Check and see if the fuel pump is working.  Doesn't take but a pin hole in the diaphram to render it useless.
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Old Hilly

Starving for fuel. When you use the choke you cut down on the amount of air getting to the engine and the air to fuel mixture gets back to where it will burn how it should but the engine will have no real power.
Check main jet in carby (water in fuel or condensation), fuel filter dirty, fuel pump or fuel lines blocked. Also check if there is a gauze filter in the bottom of the fuel tank where the fuel line conects and make certain some little critter hasn't blocked the breather hole in the fuel cap. My old Fiat tractor has problems with the gauze filter in the tank blocking up. A quick blast of compressed air up the fuel line fixes that! We get these tiny little wasps down here that build a nest out of mud inside anything that has a hole in it. There seems to be a size of wasp to match the size of almost any hole found on farm machinery, no matter how small or large. >:(

Jim_Rogers

I would check the connection from the fuel line where it joins with the gas jug. If that quick connect male or female end becomes damaged it will block the flow of fuel.

To check it take the end off the fuel line and put it right into a jug of gas and see if the mill will run correctly. If it doesn't run correctly then you'll know it isn't at that point.

Next move to the next joint in the fuel line. In my line the next spot is the inline fuel filter. They aren't that expensive. You could just change it and you'll know it's ok.
After that, check at the fuel pump and make sure that this joint is ok. I would take the in feed line off the fuel pump and lower it down and it should run gas out like you were draining your gas tank. This will prove if your line is pinched or blocked between the quick disconnect and the fuel pump. And it will make sure your inline fuel filter is flowing correctly.

Next move to the other side of the fuel pump. Take the line off the carburetor and put it into a glass jar or clear plastic bottle, and try and start the engine. If you can see that the fuel pumps into the clear bottle/jar, then you'll know it's not the fuel pump. If the gas doesn't flow then it is the fuel pump.

If it does flow properly then you may have a stuck needle in the carburetor. The old farmer's trick is to take the air filter off so you can completely expose the mouth of the carburetor. Then while it running or trying to start, put your hand over the mouth and block off all air going in. This will create a great amount of suction and it may suck the junk stuck in the carburetor through and it may just clear itself.

If this doesn't work then there should be a drain plug on the side of the carburetor bowl and if you remove that the gas should flow out and it may drain out any junk.

Next you may need to separate the top off the carburetor and using a can of carburetor cleaner with one of those little straws spray into the open ports and see if it runs clean.
You can turn out the needles out of the jet ports but you may need to count how many turns you're turning them so that you can turn them back in the same amount. After cleaning it out, you could then put it all back together again and try it.

Good luck with your repairs.

One other note, don't run your mill out of gas. This will allow your fuel line in your gas jug to suck up junk in the bottom of your tank.
Watch your tank and when it gets to the bottom, stop and refill the tank, before it runs out of gas. This is one of those things that they say "don't ask me how I know".....

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Al_Smith

It's been years since I turned a wrench on an Onan engine so the following may or may not apply .

Assuming the engine uses a diaphragm type fuel pump it would not come as a surprise if in fact the diaphragm and check valve assembley might have stiffened up just like they do on a chainsaw because of the ethanol content of the gasoline .On that in the last several years I've had to replace said assembleys on a few Briggs and Stratton engines .Not a big deal if that is the problem and a  relatively inexpensive fix .

I'd imgine if you "Googled "the engine number you might be able to find a parts list in addition to an on line supplier .

Peder McElroy

Thanks everyone for all the tips. I'll try all of them untill it works again.

pineywoods

Another common gotcha is the quick disconnect where the fuel line connects to the gas tank. There's a small O ring inside. Bad O ring lets air leak in, the fuel pump sucks air instead of gas. I had so much trouble with mine, I finally removed the quick disconnect and replaced it with a brass fitting and a hose clamp..
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Jim_Rogers

Piney:
I had the same problem.
That's why I said to start at the gas tank connection and eliminate it first, by disconnecting the gas line and running it into a jug of good gas directly without using the fittings.
I had to replace mine more than once.
I use the setup you get from parts stores for outboard motor fuel tanks or similar quick disconnect systems.

Jim Rogers

I think the method I described was told to me by the tech guy at WM over the phone. Start at the source "fuel tank" and work your way to the carburetor.
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Buck

I too would start at that quick connect. I rebuilt the carb and found that to be my problem after. :-\
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Peder McElroy

I got it to run today by squezing  the bulb on the gas line and a new filter,but still not right. Do you think a dull blade would cause the motor to work too hard and heat up? It runs good at first and then 1/2 way through the log it runs bad (after about four cuts).

WH_Conley

I had a crack in an old fuel line one time, let it suck air, run, but, not right. Black tape got me through the day. Another thing that happened was the squeeze primer in line had a valve stick. Ran out of gas with a full tank. The give away was that the bulb was flat. Smack it with something and it would loosen the valve and work fine.
Bill

Migal

Well the having to use the choke to keep it running is the dead give away to me now is it the fuel pump or plugged jet or sticking float should be a easy repair the idea of keeping it running by squeezing the primer bulb only tells me you can force enough fuel to keep it running no power tells me the mixture is not correct air leak is almost out of the equation due to fuel would leak when you primed it and one would notice. GL
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DouginUtah

No one has mentioned to check the gas tank cap. If the vent is mostly plugged it would be starving for fuel after running for a while.

Try running with the cap off.
-Doug
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There is no need to say 'unleaded regular gas'. It's all unleaded. Just say 'regular gas'. It's not the 70s anymore. (At least that's what my wife tells me.)

---

beenthere

Quote from: Peder McElroy on August 07, 2012, 06:13:29 PM
........ Do you think a dull blade would cause the motor to work too hard and heat up? ........

Is the blade dull?
south central Wisconsin
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woodmills1

take the top of the carb off

bet you find rusty debris in the bowl

use a paper towel to soak it up and out, or an air hose if you can

put the carb top back on,  the gasket should be fine as long as you are careful on remove


10 to 1 it is fine


every 2 tree years on my onan 24
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firecord

Inside the bowl there is a jet dead center.  (high speed jet) take a small flat blade screw driver and remove the jet.  you should see ligh. through the center. if  you cant see light take a troch cleaner and run it through the hole. reassemble. and it wlll be fine. thi is the primary cause of your problem

Chuck White

Quote from: DouginUtah on August 07, 2012, 06:32:50 PM
No one has mentioned to check the gas tank cap. If the vent is mostly plugged it would be starving for fuel after running for a while.

Try running with the cap off.


I had a similar problem Doug, and I would get about 2/3 the way through a cut and the engine would die unless I stopped the feed and shifted to idle.

Come to find out, my off-bearer had closed the vent on the gas cap and I never close it.

Gas tank was partially collapsed and the primer bulb was flat!

Didn't take long to figure out, only about 3 or 4 cuts!  ::)
~Chuck~  Cooks Cat Claw sharpener and single tooth setter.  2018 Chevy Silverado and 2021 Subaru Ascent.
With basic mechanical skills and the ability to read you can maintain a Woodmizer  LT40!

Migal

 :D Them Dang off-bearers they will do anything to slow down production  8) Already stated my thought's so am  Interested in what is found to be the cal prate  :-\
Stihl learning and picked up my Log Master LM2 Cat 34hp 02 21 12! 230MF+ the toys that go with it! MS361 MS271 Stihl PB500 Echo 48" LogRite 16ft Bass Tracker Pro' Abua Garcia 5600 bait caster, Wood working equipment' Lake Lot never enough time! oh don't forget the fridge with ale! Loving Wife Rebeca

bushhog920

main jet is clogged in the carb. see this all the time.

Peder McElroy

Today I took the carb off cleaned all the jets/float not sticking/new fuel filter/fuel lines are good/Gas tank clean/new fuel. Put it all back and it still runs like S---. I just don't know what to do next.

ladylake

Quote from: Peder McElroy on August 07, 2012, 06:13:29 PM
I got it to run today by squezing  the bulb on the gas line and a new filter,but still not right. Do you think a dull blade would cause the motor to work too hard and heat up? It runs good at first and then 1/2 way through the log it runs bad (after about four cuts).

If you have gas getting pumped or flowing to the carb and the carb is clean and it makes 4 cuts before acting up I'd try a new coil.  Seems like the Onan's have quite a bit of trouble with them, if not the coil you'ld have a spare one .   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Jim_Rogers

You do need to check the coil or spark plug wires.

I went through the same thing once with a high priced tech here, and after we went through everything with the gas, as you have, we found a bad spark plug wire end at the coil. I got a new coil and wires and dropped them in and it was fine again.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Magicman

If it will only run with the choke on, then the problem is the carburetor.  You either missed a jet or the carburetor cleaner just did not get to the problem.  It is usually the long brass jet assembly that screws in from the bottom.  After removing it, you may have to soak everything in carburetor cleaner.

Kohler carburetors seem to be the worst and hardest to clean.  I had a Kohler a couple of months ago that I simply had to replace, and Kohler carburetors are expensive.  About $150.  :-\
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