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Discussion Starter #1
I usually try and go through ALL the earlier post when I join a new group and have a problem. But this time I'm short on time due to the purchase of a $300.00 part that I thought was going to solve my problem but didn't. I can return it to the vendor but since it's an electronic item I'll have to pay a restocking fee so I want to be sure I don't need it before returning it.

My problem is I have one cylinder on my engine that is not firing. I've got a service manual for the Yanmar gas engine but I'm not getting anywhere solving the problem. The reason I thought it was the ignition transistor is it didn't check out as listed in the manual but when I installed the new unit I still had one cylinder not firing. I've gone through all the other tests but didn't pay much attention to readings just looked for continuity. I guess my first question is does the unit have to be mounted to the tractor in order for it to work properly or can I just connect the two plugs and try it that way?

Thanks in advance for any response. Fortunately I have a Kubota zero turn I can keep up with my mowing with but I have to have the Deere running this fall to pull my lawn vac and pick up leaves.
 

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You can just plug it in for a test run. You need to also check the 3 triggers mounted around the flywheel which tell the transistor module when to fire. The manual has a checkout on that too. Finally have you check the coils primary and secondary (resistance check)? That too is in the manual. Then there are plug wires and the sparkplugs to be checked also. Please be as complete as possible going through each section as you check and test. be patient your will get it.
 

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Discussion Starter #3
I've got a TM1277(1/88) manual and have gone through the troubleshooting for a misfiring cylinder from the beginning. I thought I'd found the problem and purchased a new ignition transistor unit but when I installed it .... same problem. So now I'm back to square one. I'll start over with my troubleshooting and hope I find the problem this time.

Just for my sanity, would someone explain to me how to read the chart showing the readings for the ignition transistor unit? I read it wrong and even though I know that's not my problem I'm still trying to figure out how to read it.
 

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Your PM to me indicated that the offending cylinder was also a bit low on compression and this could easily be the root cause of the misfire. You need to do the valve clearance adjustment per the engine manual and retest the compression...see pages 10-1 to 10-3 of the below document.

View attachment Gasoline Engine-CTM12 reduced.pdf

A newer version of the tractor technical manual is also available as TM1591 which is included below in two parts:
View attachment Tm1591_first half reduced.pdf

View attachment Tm1591_second half reduced.pdf

...and one more useful document is the parts catalog, PC2149:
View attachment PC2149_322.PDF

Chuck
 

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Discussion Starter #5
Got my hands on a reliable compression gauge today and found all cylinders okay. With that being said I see no reason to check the valve clearances now. Unless someone can explain to me how this can be anything else, I'm saying this has got to be an electrical problem.

So now I'm back to square one. Swap the spark plugs around again just to make sure the problem didn't follow a certain plug ... and it didn't. Tried pulling the spark plug wires off one by one and problem is still with the same cylinder it has been since day one. Did a continuity test on the bad cylinder's pulsar wire from where it plugs into the four wire connector right after the pulsar back to where it plugs into the transistor module and it's good. I guess tomorrow I'll try swapping the wires from the coil of a firing cylinder to the non firing one. Thought for sure I'd done this before but I've slept since then and I'm grasping at straws now. Suggestions?
 

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Time to check the pulsars out, find the one tied to the bad cylinder. You should see a pulse voltage when the flywheel gets to it. Check you manual on how to check it out, especially wiring, connectors, etc
 

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Discussion Starter #7
Thanks for sticking with me on this problem. I've checked and rechecked the pulsars half a dozen times. The only test is with a test light to show the pulsar is breaking the circuit to provide the high voltage spark at the plug. Resistance readings are the only values given to check the coils other than a continuity check here and there and everything checks out. I did a continuity test today on both wires coming off the coil of the bad cylinder back to the ignition module. No problems there.

One interesting thing I noticed was when I swapped the spark plug wires between a firing cylinder and the bad one, I could hear and see the spark at the cylinder that hadn't been firing but could pull the cap completely off the plug and not effect the rpm(s). Also, at the same time the plug wire from the cylinder that hadn't been firing did not fire on the previously firing cylinder. It was like the engine was running on 1 cylinder but not near as rough as you would expect.
 

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Discussion Starter #8
Am I correct that the spark plug wire on the 322, from the coil to the plug, is permanently attached to the coil? If so, how can the wire be checked for continuity?

Also, I have a brand new JD ignition module (AM876024) for the 322 that I would like to sell. I know what I paid for it and will sell it for less than you'll buy one anywhere else. You can email me if interested.
 

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It appears to be permanently attached according to JD Parts. I didn’t notice on the one I used last winter.



That said, I don’t see swapping plug wires helping troubleshoot anything except having 2 cylinders not firing at the correct time.

Have you bought new plugs and plug boots, or are you just moving them around?
 

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buy new plugs at a minimum
 

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Success!!!

Don't know if anyone cares but my 322 is now hitting on all three cylinders again. Turned out to be a bad ignition coil.
Just a couple of things I want to say here that may help someone else down the line.

You can't swear by EVERYTHING you find in the tech manual. Personally I find this very disheartening. My problem started the first week of the month and since then I've been through the troubleshooting procedures at least half dozen times trying to figure it out. I checked the bad coil more times than that and each time got the same "thumbs up" readings with my meter. What finally prompted me to try a different coil was I'd already made the cardinal mistake of replacing the most expensive part first. I came to the conclusion it was the ignition module after conversing with more than one technician employed at different JD dealerships in the area. Since that WASN'T the problem and I'd checked everything the manual said, it was time to start replacing the rest of the parts in the system. Granted the cost of a pulsar is less than that of a coil BUT, since I was getting the "blinking light" when using a test light and I wasn't ready to remove the parts to get to the pulsar, I opted to try the coil first. "Thank you Jesus" it worked.

I want to thank everyone who tried to help me. Hopefully this note will save someone else the wasted money and time I spent trying to solve what turned out to be a fairly simple problem.
 

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Glad you got it sorted out! How different were the "bad" coil readings from the other two? Perhaps it was and internal arcing that would not show in a resistance test...

Chuck
 

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Discussion Starter #14
Don't remember for sure but it was VERY minimal if any. I'm sure it was within the guidelines listed in the TM or else I would have been suspicious from the get go. I was using an inexpensive digital meter which I'm sure isn't in anyone's tool box at NASA. Haven't checked it yet but I'm wondering if the wire from the coil to the plug was bad. Don't know if they use a carbon or copper core in it. Since the wire is permanently attached to the coil you can't test for continuity unless you jab a probe through the insulation which leaves you open for the spark to "jump" out of the wire. I usually lose sleep over things like this, not knowing EXACYLY why the cylinder wasn't firing. But in this case I'm so glad it's running smooth I'll sleep fine.
 
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