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Message |
    
Nate Johnson
Member
Username: Wingrider
MN
Registered: 6-2007
Post Number: 393
| | Posted on Monday, July 19, 2010 - 10:52 am: | 
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Hey All,
Well, the 318 story just gets a little better each day!  I bought this 318 with a P218 that has a knock...it isn't very pronounced, but there is something not right. It acts like it the cylinders are sync'd, and fight each other.
At any rate, I got the deck in good working order, and it has cut the grass a time or two without any real trouble...noticed the pto switch was seemingly a little finiky, and a couple throws would get it to start. Yesterday evening I was just starting up to mow, and the neighbor guy needed a hand, and said his 12 y/o boy would like to cut my grass while I helped him.
I instructed him on how to use it, mentioned that it does smoke a little, but he could do the wide open areas, and leave the tight turns for me. Also told him if it made any bad noises, or smelled funny to shut it off.
Well, after a while, I could hear him mowing, and then the motor shut off. We were just about finished up with what had to be lifted, and the kid came over and said that there was a problem with the mower.
We walked up and I see smoke wavering out of the hood. He says that the deck quit cutting, and as he pulled the throttle down, it quit. It has a strong burning smell to it, which I took to be something in the PTO assembly. Knowing better than to grab ahold with bare hands, I spit on the pulley, and it boiled...obviously very hot. 
We had to pull it back to the garage, as it would turn over, but not restart. I haven't had time to tear into it, but I'm assuming the PTO is shot. The kid feels bad about breaking, but I downplayed it a bit, as he's a good kid...apparently just can't smell!
What can smoke inside these PTO set-ups, and would it kill the motor if the PTO bearing is fried?
Thanks for any help! |
Chuck Van Dusen
Member
Username: Chuckv
OR
Registered: 1-2007
Post Number: 3790
| | Posted on Monday, July 19, 2010 - 11:39 am: |
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Nate,
There is a coil winding inside the PTO that provides the magnetic field needed to pull in the clutch plate and engage the unit for power transfer. This coil can become shorted due to mechanical abrasion by the moving parts if the bearings have too much play/wear, and also have been known to internally short due to overheating and age.
Your above statement that you had to attempt to engage the PTO multiple times to have it actually work ("couple of throws to get it to start") would indicate that it was likely out of adjustment with too large of an air gap, or perhaps the coil was already partially shorted and caused the weak/intermittent engagement.
You can disconnect the PTO from the tractor's harness and measure the resistance -- most likely it is now about a dead short, but nominally it should be in the range of 3.5 to 4.9 ohms. You will need to replace the coil assembly at a minimum, and perhaps the entire PTO.
Here is the wiring involved in the PTO function.
Check the F2 fuse, if it is blown the ignition will not fire even though the engine cranks. Also be sure that the PTO switch is off, the hydro is fully in the neutral slot, and the parking brake is set if your tractor is a late model one and the brake switch is present. Note the #710 purple wire is part of what allows the spark to work if no one is on the seat but the tractor is in neutral, etc. Here is the wiring for the ignition system, followed by the cranking circuit itself:
Hope this is of some help in getting you started in finding the root cause of the starting issue.
Chuck |
Nate Johnson
Member
Username: Wingrider
MN
Registered: 6-2007
Post Number: 394
| | Posted on Monday, July 19, 2010 - 12:03 pm: |
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Thanks Chuck!
I was looking over the service manual I picked up for it while at work here, and noticed the little fuse on the diagram.
After reading a bit about air gap, it would make sense that this is/was out of adjustment. I first attributed the troubled switch as just one that hadn't been been used in over a year, and had sat outside...but now it's pretty obvious that isn't the total case.
I figured as soon as I rounded up some time to work on it, I'd pull the PTO off, and see if the fuses are good, and see if it'll start. Maybe it'll run like it should without the PTO!
Out of curiosity, when does a model become a late model? I've always assumed it was the last few years of production, but I guess I've never known the real answer. My 318 is an 87, so I'd place her as an earlier model with a P218. |
Chuck Van Dusen
Member
Username: Chuckv
OR
Registered: 1-2007
Post Number: 3793
| | Posted on Monday, July 19, 2010 - 12:29 pm: |
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Nate,
The 318 was in production for quite a few years (1983 through 1992) and had many running changes to various parts/functions. The brake switch was one of the latter changes and was on tractors above SN 600,305 in mid-1989, so it is not on your tractor.
The change to the REV4 hydro linkage was in mid-1991 and would be one of the latest updates to this model tractor...
Your 1987 tractor was the first year with with the P218 version of the engine (with the electronic ignition) so it is considered by many as a "later" model as the earlier B43 engines with the points were made from '83 to '86. The engine upgrade to the P218 version is one of the most noticeable of the many changes to the 318.
You will not need to physically pull the PTO off the tractor to continue to troubleshoot your recent starting issue -- just unplug the PTO from the harness at X26.
Chuck |
Nate Johnson
Member
Username: Wingrider
MN
Registered: 6-2007
Post Number: 395
| | Posted on Monday, July 19, 2010 - 1:15 pm: |
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Thanks again Chuck!
I didn't find a switch on the brake levers when I first looked it over, so I assumed that this one didn't have it. Unfortunately, a prev. owner did some "custom" wiring. Someone took the seat switch off, and jumped the wires, so I'll need to get one of them, but I think the other switches are in good shape.
I figured I'd pull the PTO off simply because of how much it smoked and how it smelled...figured there is a pretty good chance the whole thing is toast. |
Vinnie Hueber
Member
Username: Vinnie110
NY
Registered: 9-2004
Post Number: 1048
| | Posted on Monday, July 19, 2010 - 9:07 pm: |
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If you have an Ogura clutch the coil, most likely the part that burned up, is available as a separate part, check JD Parts. |
Steve Hayes
Member
Username: Steveh
VA
Registered: 5-2004
Post Number: 1711
| | Posted on Tuesday, July 20, 2010 - 8:10 pm: |
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I'm reading this and thinking the bearing may have seized generating the heat and smell. These clutches can be serviced, I recently replaced a bearing in one and a coil in another. The tech manual says to test the coil by removing the pulley and friction disk then a standard end wrench should stick on the surface of the field coil when it is energized. |
jason halouska
Member
Username: Halouska1
NE
Registered: 5-2009
Post Number: 30
| | Posted on Wednesday, July 21, 2010 - 9:59 am: |
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As a caveat to this (not to hijack), mine just burned up last night. I had previously set the air gap to 0.018 and mowed several times with no problem, (it was a long way out before and wouldn't engage all the time) I began mowing shut off the PTO to move something and it wouldn't engage, it also smelled funny.
I checked the air gap and it was way out again! I made one pass and it smelled real bad and was smoking, pulled it off and it was completely melted. I ordered parts, (bought coil from a JD dealer on EBAY) but something caught me as funny. In my 317 there was a thrust washer between the clutch plates and this one did not have anything.
JDParts shows an "armature" (#6 if I remember) which looks like a slip tube that goes over the crank with a ridge in the center like to serve the purpose of the washer on the 317. It runs 255.00! Basically am I missing a washer or the "armature" in my PTO? I know this would not cause the PTO to back off and increase gap (probably bad locking nuts mine didn't have the lock washers like JDParts diagram shows either)
What would cause these things to burn up like this? Too much gap, not enough gap, too tight of a drive belt throwing the assembly off, bearing rubbing? I don't want to buy these things all the time! PS ser # 429619 JD 318
I as well as Nate I'm sure, would like to know! |
Chuck Van Dusen
Member
Username: Chuckv
OR
Registered: 1-2007
Post Number: 3800
| | Posted on Wednesday, July 21, 2010 - 10:59 am: |
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Jason,
Your early 1987 318 tractor may have had that PTO since it left the factory, so it is unlikely that you will need to repair/replace the PTO "all the time" but it is a rather expensive assembly. The AM100847 "armature" assembly (#7) is pretty much everything that is not the coil and rotor, and includes the little hub/sheave you mention as part call-out #6 which itself does not have a separate part number or price.
What condition are the bearings in on your PTO? Bearing failure is the most likely cause of not keeping a consistent gap and also would allow moving parts to rub through the potting on the coil causing a short and the electrical burnout.
If neither you nor a PO has ever disassembled the clutch it will have all the parts it should have to function properly. Note that the PTO that came with your tractor was the single wire coil assembly version but you can easily convert to the later two wire one with the adapter harness that is part number AM104901.
Chuck |
jason halouska
Member
Username: Halouska1
NE
Registered: 5-2009
Post Number: 32
| | Posted on Wednesday, July 21, 2010 - 11:16 am: |
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My bearing spins freely, doesn't make any grinding noise, and didn't seem to have any fore or rear play. It does have two wires already.
One thing I noticed is that when I removed it earlier (to repair an oil leak) was that when I replaced it and tightened up the crank snout bolt there appeared to be a gap between the large washer and the bearing face. I figured this to be normal as when you tighten the adjustment bolts the pulley face would have to move on the crank away from the washer to suck up the excessive air gap??? Maybe I am wrong, but that is also why I thought maybe I needed that washer inbetween the clutch faces or that part #6 that I do not have. Does yours have the #6 or a washer inbetween??? |
Chuck Van Dusen
Member
Username: Chuckv
OR
Registered: 1-2007
Post Number: 3802
| | Posted on Wednesday, July 21, 2010 - 11:44 am: |
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Jason,
My recently acquired 318 is a 1992 year model and has about 700 hours on it. It had a bad stator when I got it and was not charging, so i had to pull the engine and take off the flywheel to replace the stator. When the engine was out, i removed all the tin and cleaned the engine up a bit. Just because there was some oil down on the frame (turned out to be from a the filter area...) I did pull the PTO off and check the torque on the front seal plate. As I recall the PTO stack up was pretty simple but you had to be careful to get the key in just the right place or the parts would not seat correctly on the shaft. I don't remember any large gaps between the retaining bolt/washer and the end of the shaft. There does need to be a small space there so the washer seats/presses on the bearing inner race to retain it without bottoming out on the end of the shaft.
I will send you some information from Ogura that might be of some help as they include some section views of the mounted parts on a crankshaft...
Chuck |
jason halouska
Member
Username: Halouska1
NE
Registered: 5-2009
Post Number: 33
| | Posted on Wednesday, July 21, 2010 - 2:27 pm: |
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Thanks Chuck! |
Neil Paku
Member
Username: Neil
NY
Registered: 12-2009
Post Number: 120
| | Posted on Wednesday, July 21, 2010 - 2:57 pm: |
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Chuck,
I'll take some of that Ogura info if you are able too please. I've rebuilt the front and rear ptos on my 430 so I'm familiar with the components but if Ogura share any more useful tidbits, that'd be great.
Cheers,
Neil. |
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