[inspired_metal]

While mowing with my 317K the PTO shuts off while mowing and doesn't want to restart. Once the engine died and would not restart. I checked the circuit and everything was working right except the switch. I replaced the PTO switch with a new one. It was then I found that both IGN (pink and yellow) wires on the key switch that go to the safety and PTO switchs were melted some and touching. I replaced the bad spots and put in a new key switch. Thought I had it. The PTO still cuts out while mowing.
Heres my question. Is this the way a bad PTO acts? How can I test that? Is there a circuit breaker in that system or fuse that I can't see?
Just point me in the right direction.

Thanks,
Dom

 

[chuckv]

Dom,

Have you adjusted the air gap on the PTO? If it is much larger than specification it will have difficulty in engaging, particularly when the engine is hot. The nominal gap is 0.018 inches.

If your issue is PTO dropout and not just a re-engagement issue, then very likely the internal winding on the PTO is opening (or shorting) as everything heats up. These PTO windings can fail over time/heat (and even abrasion if the bearing wears enough for the moving parts of the PTO to contact the coil face.) A simple test is to measure the resistance of the winding -- it should be in the range of 3.5 to 4.9 ohms or so. Usually the failure mode is for the resistance to go down due to internal shorts in the coil and excessive amperage is drawn. In later tractors a fuse may get blown, but on the 317 there is only the self resetting circuit breaker. If it was tripped by a heavy PTO current draw, the engine would die as you described. The circuit breaker resets itself in about 30 seconds or less once the load is removed...

Let us know what you find, below is the very simple wiring diagram of a 317 tractor if you don't have it handy.

Chuck

 

[inspired_metal]

Thanks Chuck,
I checked the air gap and set it at .018. Wasn't sure if a bad pto clutch would overheat the breaker or not. I'll check the windings tomorrow and see what it reads.

 

[chuckv]

Dom,

Remember it may not read abnormally low resistance until the unit has been heated up by the engine coming up to temperature -- so if it seems normal when cold, just mow with it until it fails and make a quick meter measurement at that time.

Chuck

 

[woodpecker41]

Dominic since the PTO is electric you may have a charging system going bad. Check with another persons help what the battery voltage is with the engine running and the engine at mowing speed. It should be 13.5 to 14 volts and if it isn't you need to fix it so it is. The PTO is basically draining the battery. Roger

 

[inspired_metal]

this afternoon I tested the PTO clutch on my 317. While I was testing the resistance I could smell Electrical system overheating. After resetting the gap 2 .018 it would still shut off the tractor after a few seconds. I could shut off the power take off and it would restart. Didn't like the smell I was getting so we pulled the PTO off and it looks like the part that has the wire in it was overheated and it is leaking. I'm assuming that it needs to be replaced I will post pictures later tonight. Someone let me know if I'm on the right track Thanks

 

[jdmaninlouky]

Dom -I think if it was a snake , you'd done been bit by it . Also ; the PTO "Field Coils" don't leak unless it was residual from the main seal leaking at the engine , or somewhere else motor related .

Dave

 

[inspired_metal]

Here are the pictures.

The first shows a spot where the field winging is opened up and maybe burnt a bit.

Then there is a shot that shows a sticky substance leaking down the coil.

The last is the inside of the rotor that has a gunky almost burned oil on it.

Now what do you think? Shot?

 

[tommyhawk]

Yep, it's cooked. The gooey stuff leaking from it is probably the potting material or the enamel from the wire winding. It appears to be the Ogura model clutch and you can buy just the coil for them. They are over $100 at Deere now. I don't know if you could do better than that on a web search.
Clean and inspect the other parts. Make sure the bearing, also replaceable, turns nice and smooth.
While the clutch and coil is off, clean the crank seal area and run the engine a while to see if there is any oil leaking from around the seal. Yours doesn't appear to be a problem yet, but you will know more after doing the above.
Good luck with the repair.

tommyhawk

 

[tommyhawk]

Something I forgot to mention. In the service manual is a caution to "center" the coil with the rotor. Not much more of an explanation in the book as I recall, but the rotor must not rub or drag on the outside shell of the coil. The punched out tabs on the back of the coil will normally center it in the seal bore, so I'm not sure if any misalignment will occur.
Just to be sure, a trick I use is to mount the coil leaving the bolts just a little loose. Leaving the key out, put 3 pieces of match book cover (cardboard about .025" thick) between the coil and rotor. Tighten the bolts. Remove the cardboard and make sure the rotor spins freely on the crank. If so, proceed with the assembly.

tommyhawk

 

[inspired_metal]

Thanks Tom and Chuck.
The bearing sounds a little dry too so depending on what I replace it with I'll probably need a new one. I've replaced them before. I think I'll check here with a want ad and see if there is one around the WFMers parts pile someplace.

Thanks again

 

[inspired_metal]

Chuck, Roger and Tom
I replaced the field coil with new and am back up and going. K.B sent me two he had just in case I could get one to work but they were both very low resistance. Opted for the new route instead.

Thanks for your help.