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The Onan In My 446 Quit Running


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#1 Delmar ONLINE  

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Posted December 15, 2012 - 01:16 PM

I was using the 446 to move a trailer(empty) in the back yard. It was just sitting there idling when the motor squealed and quit immediately. It was not locked up, but would only turn over slow.,.The oil level in the motor was fine, because I had checked it before I started it that morning. I checked it again when this happened and it was still good.
I charged up the battery, tried to start it, no go. I checked compression on both sides, good there too. I took off the starter, connected it straight to a battery and it spun great. It is a new starter, because the old one would not turn the motor over very good. I put the new starter back on, and I got a car battery out and hooked up direct to the starter and again the motor only turns over very slow. Next I removed the heads and valve spring covers to see if the valves are working right, and it looks like they are working like they should. Even with the heads off (no compression) the motor turns over very slow.

What is going on I don't know. I had the Onan in my first Case tractor rebuilt, and that was expensive. I really don't want to do that again. If I can't get the Onan working again, I may try to see if I can move the valves on the Case (the valve for the tiller and the holding valve on the side of the tractor) over to the Massey 316. Or just part it out.

[attachment=52361:100_8729.jpg]

Edited by JBBR, December 15, 2012 - 01:17 PM.


#2 boyscout862 OFFLINE  

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Posted December 15, 2012 - 01:39 PM

How hard is it to spin the engine by hand? If you can spin the engine easily by hand when the starter is disengaged it may be that the starter is hanging up on the ring gear. Did you check that the oil is good? I've seen gas leak into the crankcase and seize the engine.
I wouldn't do any parts replacing until you've diagnosed the problem. Could it be what the crank is attached to? Good Luck

#3 John@Reliable OFFLINE  

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Posted December 15, 2012 - 01:42 PM

how cold is it? and what wt. oil in both engine and hyd system?

#4 mjodrey OFFLINE  

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Posted December 15, 2012 - 01:52 PM

I am not familiar with those tractors at all.Does it have an electric clutch on the engine ?Maybe it has partially seized.

I had that happen to my Massey with an Onan once.

Edited by mjodrey, December 15, 2012 - 02:04 PM.

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#5 JDBrian OFFLINE  

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Posted December 15, 2012 - 04:22 PM

Could it be a problem on the load side rather than the engine itself. Perhaps the hydraulic pump is the problem or the coupler between it and the engine! Good luck. That's a really nice tractor and I hope the problem isn't serious.
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#6 olcowhand ONLINE  

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Posted December 15, 2012 - 04:35 PM

Could it be a problem on the load side rather than the engine itself. Perhaps the hydraulic pump is the problem or the coupler between it and the engine! Good luck. That's a really nice tractor and I hope the problem isn't serious.


Brian may be onto something there! Maybe you should remove the hydraulic pump before you get too much into the engine.
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#7 JDBrian OFFLINE  

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Posted December 15, 2012 - 04:38 PM

The squeal he noted just doesn't sound typical of an engine seizing. I'm thinking something wrong in the hydro pump making it too hard for the engine to turn at idle.
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#8 Farmlife OFFLINE  

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Posted December 15, 2012 - 04:52 PM

I hope ya get it fixed, sure is a sharp lookin GT
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#9 Delmar ONLINE  

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Posted December 15, 2012 - 04:56 PM

mechanical clutch for mower blade drive, deck is not on it, nor belt.
hydraulic drive. I will look into the hyd. pump. thanks for the ideas, guys. Yea, it is a cool tractor. The guy I got it from Grandpa ordered it with the options it has on it. He said his grandpa traded in his old 446 for it.

#10 timtractor OFFLINE  

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Posted December 15, 2012 - 06:19 PM

It to me sound like the crankshaft bearing. Either the bearing is wrecked or it could be the passageway from the oil pump to the bearing got pluged and is not letting oil get to the bearing. Being you said that it was idling, it could be the oil pressure could have got too low

I have had a crankshaft bearing lock up on my two cycle snowmobile. After it happened you can just barely turn the engine over.

My guess is that the bearing behind the flywhell went out. It has the most weight pressure on it.
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#11 Delmar ONLINE  

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Posted December 16, 2012 - 10:44 AM

Senior moments are allowed, yes? The idea of a pressure build up made me stand back at take a better look at the situation. That's when I noticed that the 2-way valve on the back (for running the tiller) was engaged. That seems to be what was making it too hard for the motor to spin fast enough to start.
oops, my bad.
I am very glad I have friends here that see what I don't see. Thanks guys. I appreciate your help.

Edited by JBBR, December 16, 2012 - 10:47 AM.

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#12 olcowhand ONLINE  

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Posted December 16, 2012 - 11:23 AM

So she's running fine again? Did you possibly hit the valve getting off the tractor & not realize it?
And if senior moments/brain-farts weren't allowed.....we'd ALL be in trouble! :D
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#13 Toolpartzman OFFLINE  

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Posted December 16, 2012 - 11:35 AM

Whhhheeewww. Good news is always best
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#14 MH81 OFFLINE  

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Posted December 16, 2012 - 11:40 AM

Now there is some good news. I was hoping you'd find something simple
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#15 Moosetales OFFLINE  

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Posted December 16, 2012 - 12:21 PM

Perfection seems to be expected elsewhere on the web.......NOT HERE......thank goodness. Glad it all worked out.
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