JD316 Onan Engine Seized

[OrtisEvans]

I have a ~25 year-old JD316 Garden tractor with the Onan 2-cyl engine and about 700 hours on it.. I tried to start it recently, and it cranked for a bit and then stopped. After trying various things, I tried to turn the flywheel by hand and it is stuck. It won't turn either direction. Yes, I hit it with a block of wood and a hammer and still no-go. Yes, it has oil in the crankcase.

It ran fine a month or so ago. Does anyone have any ideas that are easier than pulling the engine and removing the oil pan? I fear that it has a broken rod, but even with that I would expect a little motion in the flywheel.

-Ortis

 

[pmsmechanic]

Here's what I would do. Repower Old Equipment at Small Engine Warehouse Go to this website and figure out what you need.

Your old Onan isn't worth fixing. Last time I looked about 20 years ago pistons were $600 each. Now you can't even find parts as Onan is no longer in business.

Edited to add: Make sure there is nothing simple wrong first before you spend big $. The electric clutch or a bearing could be seized for example.

 

[ruffdog]

Did you pull the spark plugs yet? Is it hydrolocked with fuel from a carb leak?

 

[OrtisEvans]

Thanks! I agree that it's not worth spending much money on. I did pull the plugs, buy the cylinders are dry. On the mag clutch, I was able to rotate the pulley by hand to help get the belt off. I am now working to disconnect the driveshaft just on the off-chance that the hydrostatic transmission is seized. However, without being able to rotate the shaft, the bolts are hard to get to.

The other unlikely possibility that I will check is that the starter pinion could be jammed against the flywheel, but that should have cleared when I hit the flywheel with a hammer. This machine has had repeated starter alignment problems.

My curiosity is piqued now, I want to figure it out if I don't have to waste too much time doing it.

Question: I've never had a bearing seize with screaming first. Do engine bearings ever do that?

-Ortis

 

[radios1]

most likely, the starter gear could be jammed against the flywheel. especially with repeated starter alignment problems. try removing the starter.. I had this happen to a briggs recently, the starter gear wanted to keep riding up past where it's supposed to..

 

[ruffdog]

My first onan had a cracked aluminum starter mount that I welded and beefed up. I never had another problem. My 2nd newer onan has been fine so far.

 

[super55]

I agree with others pull the starter and see if it will spin.

I had an old jeep that seized on me over storage one winter. Ended up putting about 1/2 a cup of ATF fluid down each cylinder and let it sit for a day then got it to spin again by working the main pulley. Haven't had a problem since.

 

[OrtisEvans]

After trying a few other things, I hit the flywheel a couple more times, and it rotated. However, the starter still does not engage, even with a know good battery. My conclusion: the starter pinion was jammed with the ring gear on the flywheel. Either there is high resistance in the starter circuit keeping it from engaging properly or else the starter pinion is bad. Both of those have happened before. I'll either pull the engine to get to the starter when I get ambitious enough, or else I will get rid of it. I've been dealing with issues like this for 25 years.

Thanks for the advice. It helps to know that others have similar problems. I did look at the price of a new replacement engine, and the engine costs as much as the tractor is worth.

 

[radios1]

After trying a few other things, I hit the flywheel a couple more times, and it rotated. However, the starter still does not engage, even with a know good battery. My conclusion: the starter pinion was jammed with the ring gear on the flywheel. Either there is high resistance in the starter circuit keeping it from engaging properly or else the starter pinion is bad. Both of those have happened before. I'll either pull the engine to get to the starter when I get ambitious enough, or else I will get rid of it. I've been dealing with issues like this for 25 years.

Thanks for the advice. It helps to know that others have similar problems. I did look at the price of a new replacement engine, and the engine costs as much as the tractor is worth.

that's a JD316 Garden tractor, it would cost a bundle, many thousands of $ to replace it with something equivalent new, unless you can find a used garden tractor in good shape for a good price..

 

[Richard001]

After trying a few other things, I hit the flywheel a couple more times, and it rotated. However, the starter still does not engage, even with a know good battery. My conclusion: the starter pinion was jammed with the ring gear on the flywheel. Either there is high resistance in the starter circuit keeping it from engaging properly or else the starter pinion is bad. Both of those have happened before. I'll either pull the engine to get to the starter when I get ambitious enough, or else I will get rid of it. I've been dealing with issues like this for 25 years.

Thanks for the advice. It helps to know that others have similar problems. I did look at the price of a new replacement engine, and the engine costs as much as the tractor is worth.

I say, perhaps you just need to replace the starter pinion gear and associated parts. You didn't say if the starter spins when you hit the start switch. If the starter does not spin, could be something simple as needing new brushes.

Richard