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My 322 has started to run a little weird. It starts perfect, runs great for awhile and then seems to lower rpms and and shutter a little, keeps running but smells rich. Then it might snap out of it and run normal again. Almost like it’s not firing on all cylinders but still runs pretty smooth. Is it possible for it to almost go unnoticed with only 2 cylinders firing? Not sure where to begin, check plugs for color/ wear? check fuel pump?
 

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First thing to try us run it with the gas cap loose. If the vent is plugged it will cause a vacuum in the tank and starve the engine for fuel.

Free and easy first step in diagnosis.
 

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That kind of sounds like a coil cutting out.

If you have a harbor freight nearby this is a cheap way to find which cylinder, and part swaps can confirm if its the coil.


 

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That kind of sounds like a coil cutting out.

If you have a harbor freight nearby this is a cheap way to find which cylinder, and part swaps can confirm if its the coil.


First thing to try us run it with the gas cap loose. If the vent is plugged it will cause a vacuum in the tank and starve the engine for fuel.

Free and easy first step in diagnosis.
The gas cap is only a year old? I’ll try anything
 

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That kind of sounds like a coil cutting out.

If you have a harbor freight nearby this is a cheap way to find which cylinder, and part swaps can confirm if its the coil.


I have one, should I buy two more and hook all 3 up at the same time? I was also suspecting a coil
 

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I have one, should I buy two more and hook all 3 up at the same time? I was also suspecting a coil
It’s up to you, I just test one at a time. It only takes a second of engine off time to move it.
 

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It does sound like an ignition issue... It could be a coil, the transistor module or even an failing pulsar -- each of these components can cause a single cylinder spark failure or intermittent/weak spark. Here is the wiring excerpt that shows how this ignition system is wired. Check all the connections and grounds first, as these components are rather expensive.
322 ignition wiring diagram.JPG


Chuck
 

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That kind of sounds like a coil cutting out.

If you have a harbor freight nearby this is a cheap way to find which cylinder, and part swaps can confirm if its the coil.


I have one of these and it is very useful, well worth getting, should have gotten two so as to have one in each barn where tractors are stored.
 

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Thought I would post this diagram I generated from the more detailed descriptions of the gas Yanmar engine ignition system found in the F932 manuals -- I added the 322 harness connector numbers and verified the wire colors. The color coding of the circuit functions matched with the text description in the later manual makes the function of the pulsars, transistor module and ignition coil combination far more understandable than the simple information found in the 322's TM1591 in my opinion.

Hope this is helpful...
Gas Yanmar ignition function from F932 manual (322 harness connector numbers added).jpg

Apologies for the low color contrast between the purple path coding on the cylinder #1 ignition circuit and the other black paths on the diagram...

Chuck
 

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Thought I would post this diagram I generated from the more detailed descriptions of the gas Yanmar engine ignition system found in the F932 manuals -- I added the 322 harness connector numbers and verified the wire colors. The color coding of the circuit functions matched with the text description in the later manual makes the function of the pulsars, transistor module and ignition coil combination far more understandable than the simple information found in the 322's TM1591 in my opinion.

Hope this is helpful...
View attachment 747163
Apologies for the low color contrast between the purple path coding on the cylinder #1 ignition circuit and the other black paths on the diagram...

Chuck
 

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Discussion Starter #11
This is great! Thank you!
I’ll be digging into testing today, got a new coil to swap around just in case. Man I hope it’s not the pulsars !
 
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