318 PTO won't engage

6266 Views 5 Replies 5 Participants Last post by Jpsb, Aug 8, 2009

Big_lic

Discussion Starter · Aug 4, 2009

I just had my 318 apart to change the steering control valve and upon completion the PTO won't engage. I have one wire I'm not sure about. Is there a black wire that goes from the PTO switch to the hour meter? The wire in question has pulled out of it's plug and I have two choices. The hour meter or the plug with the purple wires that also comes from the PTO switch. It also has a loop that connects two of the three wires in the plug. Thanks for your time and consideration.

Todd

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mydeskclock

· #2 · Aug 4, 2009

Todd- at first blush neither jibes with the electrical diagram. Although- if you are not the original owner, like half of us, someone may have been there before. I had all sorts of patches and replacements. Check your email- I sent you a pic of the part of the schematic that may help. Good Luck

Jim D.

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chuckv

· #3 · Aug 4, 2009

Todd,

The X5 connector with the purple jumper is for the rear PTO switch/harness when fitted -- it does not get another wire in the single front PTO configuration.

The black wire from your PTO should go to the ground harness, which is the X26 connector shown above with wire 125. The X25 connector from the hour meter is also a black wire connected to the ground harness, wire 130, so it would work and may have been the way it was when you took it apart.

I am sending you some additional information by e-mail that is too large to post here...

Chuck

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bob421

· #4 · Aug 4, 2009

Todd,

I have a 318 and was just involved in wiring issues related to the same harness. I also have a single black wire without a plug. Closer examination of the terminal revealed no markings or scratches indicating it had never been used. I checked the wiring diagram and found I had all the connections I needed so I discounted the wire as an extra ground wire possibly for a rear PTO switch.

Bob

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Big_lic

Discussion Starter · #5 · Aug 4, 2009

Thanks for the help. If I read the schematic correctly I should only have wires to four of the five posts on the PTO switch since I only have the front PTO set up. And the extra wire from the hour meter is for a ground that I really don't need for the PTO to work? So I should look at the air gap on the clutch assembly itself?

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Jpsb

· #6 · Aug 8, 2009

Todd, I had the same problem, PTO would not engage. Since I have 3 JD318s I swapped PTOs and it still would not engage. Then I swapped them back and neither would engage! So I bought a new PTO for one tractor and that worked fine. For the other tractor I just bought the big round metal part that goes inside the PTO (forgot what it is called). That would not engaged until I adjusted the gap. What I learned from all this is to check the PTO gap first! Try to tighten it and see if that helps. Also check the resistance in the PTO. It should be 4.5ish, if it is reading close to 0 like mine was you might need that big round metal part inside the PTO. $170.00ish at JD where a new PTO will cost you $350.00ish at JD. I'm pretty sure the only part that can short out inside the PTO is the big round steel part.

To sum up
Listen very carefully when you engage the PTO you should hear a slight click. If so the wires are correct. Next check resistance 4.5ish is prefect, lastly carefully tighten gap just a little bit at a time until PTO engages. Hope this helps.

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