JD 40 runs on only 1 cylinder

2510Deere · May 31, 2018

First of all, thank you to all of you writers who solved my earlier issue of antifreeze migrating into oil; and subsequent head gasket replacement guidance on torquing. All worked well. One more issue has come up:
1) Assembly completed, head gasket, etc. all carefully back together
2) Tractor started right up, but it runs hit/miss, like one of those one-cylinder Deeres.
* My work on this so far: I have new plugs (good spark on both of them), new distributor cap, new wires
* I have good spark on both plugs
* Interesting...when I pull plug wire off #1 cylinder, tractor smooths out and runs good on 1 cylinder
* As soon as I put plug wire back on -- engine bogs down and sounds like the hit/miss 1 cylinder again.
In summary, I have gone down all of the electrical avenues that I can think of. I need your expert guidance.
Thank you. Jerry

Mark-Ia · May 31, 2018

Your plug on #1 cylinder is bad. Move it to #2 and the problem will follow the plug.

Half · May 31, 2018

Even a new plug can be bad.

Barts Dad · May 31, 2018

I?d try a different plug. 40 years turning wrenches and had numerous bad plugs right out of the box. AC Delco with no threads, Champions with no center or side electrode, Bosch with hairline cracks. Good luck!

James Howell · Jun 1, 2018

Another cause could be a broken valve spring(s).

ndgregor · Jun 1, 2018

As previously mentioned, try swapping the plugs to see if the problem then follows the plug.

I have an M and a cheap thing to try is put a new condenser in the distributor. I have had brand new condensers last only a few hours, and the tractor would run terribly once they went. At times it seemed like only on one cylinder. They are a cheap and easy repair, and my experience has been you will need spares at some point anyway.

If the problem persists, look into the valve train. Did you set the valve clearances per specification when you did the rebuild? Look for broken valve springs or bent pushrods. Make sure the rocker arm assembly is getting lubrication. Turn off fuel and remove spark plugs and run the starter to visually verify valves are opening/closing properly.

old · Jun 1, 2018

Pulling the plug wire part way off and it start to fire is a sign of a bad spark plug. By doing that is causes the spark to build up a bit more so that in turn makes the foul/bad plug fire.

PopinJohn · Jun 1, 2018

There are two distributor caps that will both fit on the distributor
and the clips will engage.
One has the two spark plug nipples straddling the clip,
the other has the two nipples on one side vs the clips.
Maybe you were sold the wrong cap?

Glen D Anderson · Jun 2, 2018

As stated above, assuming the parts are correct and/or not defective, have you confirmed if the firing order is correct(plug wires hooked up correctly)?

(quoted from post at 15:53:26 05/31/18) First of all, thank you to all of you writers who solved my earlier issue of antifreeze migrating into oil; and subsequent head gasket replacement guidance on torquing. All worked well. One more issue has come up:
1) Assembly completed, head gasket, etc. all carefully back together
2) Tractor started right up, but it runs hit/miss, like one of those one-cylinder Deeres.
* My work on this so far: I have new plugs (good spark on both of them), new distributor cap, new wires
* I have good spark on both plugs
* Interesting...when I pull plug wire off #1 cylinder, tractor smooths out and runs good on 1 cylinder
* As soon as I put plug wire back on -- engine bogs down and sounds like the hit/miss 1 cylinder again.
In summary, I have gone down all of the electrical avenues that I can think of. I need your expert guidance.
Thank you. Jerry

buickanddeere · Jun 2, 2018

(quoted from post at 09:20:06 06/02/18) As stated above, assuming the parts are correct and/or not defective, have you confirmed if the firing order is correct(plug wires hooked up correctly)?

(quoted from post at 15:53:26 05/31/18) First of all, thank you to all of you writers who solved my earlier issue of antifreeze migrating into oil; and subsequent head gasket replacement guidance on torquing. All worked well. One more issue has come up:
1) Assembly completed, head gasket, etc. all carefully back together
2) Tractor started right up, but it runs hit/miss, like one of those one-cylinder Deeres.
* My work on this so far: I have new plugs (good spark on both of them), new distributor cap, new wires
* I have good spark on both plugs
* Interesting...when I pull plug wire off #1 cylinder, tractor smooths out and runs good on 1 cylinder
* As soon as I put plug wire back on -- engine bogs down and sounds like the hit/miss 1 cylinder again.
In summary, I have gone down all of the electrical avenues that I can think of. I need your expert guidance.
Thank you. Jerry

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JD 40 runs on only 1 cylinder

2510Deere

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Mark-Ia

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Half

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Barts Dad

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James Howell

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ndgregor

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old

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PopinJohn

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Glen D Anderson

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buickanddeere

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