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john deere 318 help, i think the Onan is done for good?

22807 Views 103 Replies 28 Participants Last post by  alfieepstein
New to this forum, and i must say it looks fantastic! lots of helpful people, and lots of great tractor stuff. I bought my "new" 318 in the fall. My first real garden tractor. I searched for quite some time for a machine that could bag vast amounts of leafs, and clear alot of sloped, fairly steep, slippery driveway, and decided on this 318. came with power blower/catcher for leaves and the auger snowblower. It did a great job with the leaves. I was so excited to plow the driveway on this first winter storm in chicago. Well, i tried plowing without the chains, (1st mistake) and the driveway was too slippery, so i went to go get the chains and while doing that, the engine started sounding different, almost like it was on choke. Well, the engine then quit, and now won't start. The starter seems to want to crank it over, but can't so i get a grinding noise. I fear the worst, a siezed engine. There was oil in it, my only concern is that it was parked on a hill for a while, could the oil have drained back leaving no lubrication? is there an oil pump on these Onan engines? I am fairly mechanical, but haven't dealt with tractors too much. Usually if instructed well i can find the problem. my question now is, where do i start? What can i look for to figure out if this engine is done? I'm assuming that since it started ok that it is nothing electrical, and the snow thrower wasn't on and it was in neutral so i don't think its anything related to those two issues. I'm just praying someone with a good knowledge of these machines has seen this before. I don't really want to have to start the post of "so what's the best repower engine" :banghead3 although i'm pretty sure that that is coming.
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ok, i dont know if anybody is still on this link, if i don't get any responsed i will post a new link. The tractor is running...there's the good news. Now the bad news. It's definantly not running right. I now finally got to mow the lawn with it "fixed" and she certainly wasn't running like she used to. First off, the tractor is much louder, and rougher sounding. 2nd, it's vibrating like crazy everything is vibrating, motor steering wheel even the fender. 3rd. It doesn't seem to have the same smooth throttle that it used to. When you would increase the throttle it would move up at a nice even pace, now it seems more choppy. Finally the big one, it definantly doesn't have the same power when it is "working". I couldn't notice before when just testing the machine out, but now when i have a deck on, the pto engaged, it doesn't have near the power it used to. It's bogging down, even dying on hills, and it just seems like its working really really hard to do what it used to do effortlessly. Again, i don't know where to go with this, does anybody have any suggestions? The only things different than when it ran great originally are these.....I put on a used genuine Onan starter instead of the cheap knockoff (would seem irrelevant to it running bad). During one of the many times pulling the motor, i ripped the wire out of the condenser, but i had a used spare condenser so i put that on (plausible that this could maybe have something to do with it?) 3rd, new plugs, they are AC Delco R44LTS. I do have new plugs coming in the mail NGK TR5. my dad got the delco's, but doing research online i'm not 100% that is a compatible plug. Could any of these things be a problem? Also, when starting the thing, It's starts up fine, virtually right away HOWEVER, it still doesnt sound like it used to when you turn the key. It used to sound real smooth, now its loud. My guesses, and they are pure guesses are these, something is still wrong electrically causing the bad starting noise and maybe uneven voltage?? or that something is misaligned somewhere, or finally that my pistons are going, which would mean low compression and possibly the vibration? any thoughts? Also, would a video of the thing being started and ran be of any use? I could probly swing that if people think it would be helpful.
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A brilliant idea! Thank you Leine! Why didn't I think of that? It is running on one cylinder. Pulled the plug wire on the left side and it died. I pulled the plug wire on the right and nothing happened. So the problem is finally diagnosed.

So what can be the possible causes for a dead cylinder?

I pulled the plug on the bad cylinder. It was wet with fuel which makes sense. However, i dried it off and started the machine with the plug out. I put the plug close to the block and i most definantly have spark.

That leads me to believe that the plug, plug wire, and ignition coils are ok. Am i correct in this assumption? If so, then the what other possible cause could there be?

Seems to me the only other problem would be bad compression which would mean
1. Bad piston rings
2. Stuck valve (i can only hope)

Any others possibilties? Correct me if I am wrong but i don't think it could be a bent crankshaft or connecting rod as this would cause problems for the other cylinder as well and it shouldn't be able to run at all.

I think my dad has a compression gauge, so im gonna go grab that this afternoon if I can find it to make sure compression is my problem.

My final question is this, What would be the cause of the rings going bad if that is what it is?
Is there a root cause that needs to be fixed to prevent this from happening again?

Also, at this point is it worth pulling the engine apart to replace the rings, is it likely that the other cylinder would go soon too? If one set goes bad, does this mean that I should just overhaul the whole thing?

The engine has 745 hours on it, seems to me most people around here say an Onan should last to at least 1500 hrs. or so which makes me think it might be worthwhile to do.
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The problem is definantly compression. I tested and I'm not getting any compression whatsoever on the right side. So i guess i have to start working my way in towards that cylinder. Any advice on my approach and what i should look for first?{%22pl%22%3A{%22uc%22%3A2%2C%22aid%22%3A5901328028%2C%22pid%22%3A257800663028%2C%22vp%22%3A%22s%22%2C%22sb%22%3A5}%2C%22ovm%22%3A{%22v%22%3A%22s%22}}[/URL]
ok, so i don't remember exactly how i posted a picture so if there is a few random posts with a jumbled mess i am sorry. Here's all the new information, and there is alot.

I started breaking the engine down. I got to the valves and saw both were moving so i new i had to pull off the cylinder head.

I pulled off the cylinder head and saw some not so good news.
1. Cylinder is not moving when i turn the engine over
2. When i pulled off the head water came out.....yes, water. looked like water, smelled like water, and i even soaked it up with a paper towel and tried to light it on fire but couldn't water. Also, if the picture comes up you can see surface rust starting on the top of the sleeve. indicating water. The water must have been from the previous owner, because i store it inside, and it was outside when i bought it. I'm suprised that it took that long to surface as a problem. Again i used it all fall with no issues.

So i have stopped here to see what everyone thinks i should do next. It seems to me that the answer to the problem is indeed a broken rod? Or are there other possibilities? I do have 2 extra rods and piston heads that look ok in my spare parts. So i could get the rod replaced cheap.

I'm assuming at this point i would have to do a total teardown, polishing the cylinder sleeves etc. If i can get the broken part for nothing how much would a teardown/rebuild roughly cost? Is there anything else you would need besides new gaskets? a polishing tool and the tool to get valve stems off the spring (the few remaining things ive retained from high school shop when we rebuilt a small engine)?

Finally what next? do i have to get that cylinder out next? and how do i do that? Pulling the cylinder head is easy, and i can get my hands on a torque wrench to put that back on, and thanks to alphie i have the specs :). But from a quick glance the cylinder sleeve wasn't so obvious on how to take off, and i'm not even 100% sure that is what the next step even is.

At the very least it's been a huge learning experience for me.

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ok, the link takes you to my new snapfish album with a few photos of the cylinder. It's not as good as seeing it in person, but it's something.
ok, well things have gone from bad to worse. I'm pretty sure im looking at a repower here. Essentially this is what i found.

When i pulled the oil pan i found out it was definantly the rod. The rod was shattered. Essentially what was left of the rod then pushed up and lodged inside the piston head. I managed to get the rod part out of the inside of the piston. I got the piston out and from what i can tell the cylinder looks good. I placed one of the extra piston heads i had in there and it seems to slide in and out OK.

The crankshaft has some slight damage however, i took a picture but i needed to use a flashlight and that led to a poor picture, i hope to take one in the sunlight so its easier to see because that's definantly one thing i want you all to look at. There seems to be some extra metal on the part where the rod connects that is almost fused on. I would obviously need to get that off if i were to put a new rod on. but it looks like there is pretty significant wear. So i guess my other question is how "pristine" does crankshaft need to be where it connects to the rod?

when comparing the old piston head with the extra i have, i noticed that they seem to be the same size, however the ring pattern is different. The spare pistons i have use smaller piston rings. Could these be from a B series? The rods on the spares say Onan, so they are Onan pistons, but i know that the old rings wouldn't fit on there, you can visually tell. I took a picture of that as well. So my question is could i use these pistons if they are the same size and the rod is the same size?

here is the link to the new pics
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ok, i will start breaking the entire engine down. I will try and get pictures up of everything and start asking on how to check for damage once it's all apart. Now for a couple more questions.

1. If it was lack of oil was it because it was sitting for 10 minutes or so running on a slight incline? it was on the driveway which has a slant, but not an outrageously big slant. Also there are some hills on the property so it does spend some time on hills. When i checked the oil it seemed fine, and the oil light never came on. (maybe a bad sensor or burnt bulb?) Or is it possible this damage was caused by the previous owner and it just reared its ugly head now?

2. I found a guy selling 2 pistons and a crankshaft for a P218 engine. Said he repowered and is parting out the Onan. (first off how big of a risk is it buying it?) 2nd, If I am replacing all 3 components will it be compatible with my P218? If there is a possibility it won't be, what information do i need to get to make sure it would be compatible?

3. finally after posting 1 and 2. I read the link about rebuilding from Onan parts, and its amazing. Makes me feel like i can do it. I think at the very least i will break it down and see what damage is in there. Finally, after reading that it looks like if that setup measures out ok it would work since all the parts are the same style. Now my question is if i have to machine the cylinders, does that mean i would need larger pistons? or do i just need larger rings?
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Well i have taken some time trying to get the engine apart. I think I am going to just repower. Here's the update.

1. I got the PTO off ok, but im having trouble getting the flywheel off. Is it pressed on? do i need some type of puller or am i just being too kind to it?

2. I'm having trouble getting the good piston out. It's catching on the first ring. I didn't want to start banging on stuff in there. What's the best way to get that out?

3. The crankshaft doesn't look good. seems like significant wear on the side with the bad rod compared to the other side. Also there are some gouges and marks on various parts of it presumably from parts hitting it while moving. But to me that journal on the blown side looks pretty bad.

4. I don't think that i have the expertise necessary to rebuild myself. I'm having more trouble than i thought taking it apart. (appearantly this engine isn't as easy as the 3.5 hp briggs and stratton i took apart and rebuilt in shop class 10 years ago :) )And putting together is a much tougher deal. I worry about damaging parts and making a bigger mess as i go along. I think I am just going to bite the bullet and have a nice new engine. I however, might try to rebuild this one just for the expierience and entertainment in the mean time. If not it will just be parted out to the best of my ability with the stuff i know is good.

4. Thank you all so much for your help. You might see continuing posts as i try to rebuild anyway ( will depend upon how bores and other parts are mostly. Don't mind taking the time but i won't want to spend a ton of money on an engine i probably won't use)

5. Finally, my last questions are on the repowers. I read some other posts on repowers, but am looking for a bit of fresh insight. I've done some research and I am 95% sure im going with the Vanguard. Probably the 23 hp. Figure if im putting in a new engine, what's a few hundred more bucks for a bigger one? My question is this.....

Anybody have any experience with the Vanguards? like them? hate them? Any recommendations on the big 3 replacement engines?

Also, what is in the adapter kits? How much does it take to get the Vanguard (or other engines) in place correctly? Are they parts i could fabricate myself? (mainly just brackets) or are we talking new driveshafts and things of that nature? It seems like quite a bit gets tacked on to the price when an adapter kit is included. Anybody who has repowered i would love your advice and reviews!
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@ Leinie:

Lol, i will keep that in mind and start watching craigslist. Although i probably won't replace until i need too. If i do that I am also gonna have to find some decals that say "robotractor" or "i used to be a john deere 318" :)
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