[elbrus]

I’m new here but have read and followed a lot of the archives on this subject. I have a 322 that quit while running and has no spark to any cylinder. With the key on I have close to 12 V at the positive side of all three coils. I've removed the transistor module and did a resistance check with a Fluke 335, and had significant differences with the chart in the TM-1277 manual. (See enclosed, red is disagreement). However, I'm curious if the digital ohm meter I’m using may not properly check the resistance if there are diodes involved due to the small current involved. I’ve not seen any reference to that mentioned.
As far as what else it could be I guess all 3 pulsars could be bad but that seems so unlikely. What else should I be looking for?
Thanks in advance for any advice/help.

 

[chuckv]

Bernard,

Welcome to the WFM forums! Have you had this 322 for some time and it just recently quit, or is this symptom something the tractor came with when you acquired it just now?

The table you show above has a text note that accompanies it in the TM1591 that states:

"The resistance value shown is *an approximation.* The listed value may vary depending on ambient temperature and the condition of the ohmmeter battery. What's most important is, either there is continuity or there isn't continuity"

Where the table shows an "O" there should be some resistance detected...where there is an "X" there should be infinite resistance (no continuity...)

In your red-lined table, do your red x's indicate a substantially different resistance than the value listed in the manual, or do they actually mean that you do NOT MEASURE ANY CONTINUITY? If the former, then your module is most likely still good.

As you surmised, a digital meter may vary quite a bit from the "nominal" shown in the manual...

You might check the condition of the black wire in the connectors at each end of the harness running from X24 to X25 as that is a single point of potential failure where an open could cause no spark on any plug and would keep the voltage at the (-) side of the coils from ever switching low...

Let us know what you find, and good luck trouble shooting such an odd issue.

Chuck

 

[elbrus]

Thanks, Chuck
I've had the tractor for about 10 years. My son told it just died when it was idling. The tractor has had a couple occasions in the past few years, were it has quit but started up again after a couple hours. I’ve got a mechanical background, so I know just about enough electrical stuff to get me into real trouble. In the table I put together, X’s represent a complete open (no continuity to the limit of my meter) and the Red X is where it disagrees with the table in the manual. So it’s not looking good. Another simple way I can normally diagnose things of mine like this is look for the most expensive part to replace and I’ve found it.
I still plan to re-visit the transistor with an old analog meter (instead of a digital meter) and also look at getting a diode check on some of those leads as I notice all the symmetric (non –diode) resistances seem to check out. That concerns me if I’m not getting the right measurement. Wires and connectors all look good, but I’ll also double check the black lead connection as you mentioned and if I read the schematic correctly the black and white lead could also cause a single point failure.

Bernie

 

[elbrus]

Well for whoever is still following this, this is where I am so far. I re-tested the transistor module with an old analog volt meter. Now some of those infinite resistance readings do show a resistance. These readings with the analog meter vary drastically depending on the different scales. I'm guessing that the difference is because the meter uses a lower voltage with higher scales, and my Fluke meter applies such a small voltage that the reading on it is infinite. I wonder if the table would have been better presented as the expected voltage drop across some of these measurements in question. This transistor module is confusing to me so I need to revisit this before I can conclude it’s bad.
I did turn the key on, neutral, seat switch depressed etc. and grounded the ground terminal on coil number 1 and I do see a spark. So at least one coil is OK and it also verifies again that I get voltage to the positive side of the coil. I also back checked each of the pulsar coils from the transistor module connector. All 3 pulsar coils had an acceptable 19.2 – 19.5 ohms resistance. I did checked the other transistor connector and verified that the black/White transistor lead (which connects to the black lead to chassis ground) has continuity to ground. So everything else still seems to check out.
Plugged in the transistor module for kicks and I still see no spark.

 

[chuckv]

Bernard,

Here is the wiring diagram section dealing with the ignition on the 322:

Note in particular that the #140 black wire from the transistor module is another "single point of failure" that could keep all spark from occurring. That wire supplies the ground connection to the module, and connects through the X18 connector to the #135 black wire and into the harness splice that leads to system ground.

Ground connections on these tractors should be carefully inspected, and there is a requirement for the connection of engine ground to chassis ground due to the insulating properties of the rubber motor mounts. This ground is supplied by the braided strap shown here:

Chuck

 

[JDF/ SwampFox]

Us 322 owners stand back let our champion Chuck deal with these questions.
He's awesome help.
Thanks for posting your problem in detail. It helps the rest of us too.
Welcome to WFM Bernie.

 

[elbrus]

Chuck
Thanks for the wiring diagram. I have the older TM-1277 manual from Dec-87 and don't have or have not come across this diagram in that manual yet. I apologize if I'm not clear as I did not have the wire or connector numbers from that diagram. In my previous post of 11/04 The black ground wire that I checked continuity to ground is indeed the #140 wire to ground at the X26/X27 connector that you speak of above.
A general question, have these transistor modules been known to fail and knock out all 3 plugs?

 

[chuckv]

Bernie,

I have never had a failure on either of my 322 tractors nor have I heard of it being common. But certainly it must be at least *possible* so if you have a WFM member nearby that can loan you a known working module that would be a good way to eliminate it as your root cause in this case.

Chuck

 

[ajcan]

Bernard

Though not common I had a failure of the TDC module causing no spark.
There is a pink wire that comes off of the TDC module that provides power to the transistor module to allow it to function.
On my late model 322 there was no power on that pink wire though all of the inputs were met at the TDC module.
I replaced it with a used one purchased through a member here and the pink wire then had power and it fired right up.
Again,this is not a common issue but it was what I found and is something I would check.If the transistor module does not have power it can't do it's job.

AJ

 

[elbrus]

AJ,
I get power at the coils (pink wire) and my hour meter works, so my TDC module must be OK. But to that point I've never checked the black/pink wire from the hour meter connector X18 to the transistor module connector X26 to be sure the transistor module is getting power. So I'll do that.
Even though my pulsars check out, I also want to check if I get any signal from the pulsars so I'm looking for a scope or sensor to do that. I’m assuming a single magnet 120 degrees apart excites the pulsars so just one failure point albeit a remote possibility.
Other than that I think I've exhausted any other possibilities. So looks like I’ll be mail ordering for a new transistor module.

 

[ajcan]

Bernard

For a little extra insight go up top and click on the "search" button.
Then type in "322 transistor module".
Then go down one line and change the word "or" to "and" then hit enter.
It shows 14 other threads with those key words.Maybe reading something will make a light come on.


AJ

 

[elbrus]

I thought I’d close out the thread I started. First I’d like to thank Chuck for the advice and diagrams. It appears that you have helped a lot of folks here. My problem after performing the initial electrical diagnostics is that I found it particularly difficult to positively check my transistor module. I quick review of prior posts never found anyone who performed the test and posted their results. While the actual numbers aren’t that important, I could get no readings with a digital voltmeter bit would get diode resistance from an old analog meter. So, I ended up basically doing a reverse check on all the leads to the module which pinpointed the fault. I think this should help on any 322 problem when you do not have a spark on one or more cylinders and can verify that you are getting voltage to the pink wire at the coils. I’ve only diagnosed this one electrical problem on this tractor, so I’m not an expert by any means. I’m posting this just to give my results back, and to those so inclined as just ideas and what worked for me.

My JD 322 died while idling and I had no spark, but had voltage at the pink lead to the coils. I performed the initial diagnostics, but could not verify I had a defective module from the chart found in at least in the TM-1277 manual. I also did not have access to try and swap out with another module. Before I spent about $300 on a new one, I wanted to double check all the circuits that the module accesses. If these checked out then I felt reasonably assured I was on the right track. Here’s a summary of what I checked.

1) Leads at the X27 connector. With the Key on and all safety switches closed (seat, neutral etc.) there is 12V between the Pink/Black and Pink Leads. (Module gets power and is grounded)
2) Leads at the X27 connector. I removed the plugs and grounded them. Again with the key on, and quickly grounding the white/Blue, Black/Yellow, and White Leads one at a time, there is a spark at the number 1, 2 and 3 plugs. (Leads to the coil and coil are OK)
3) Leads at the X24 connector. The resistance between the Black wire to the Green, Brown, and White Leads are in the 19.2 – 19.5 ohm range. (Leads to the pulsars are OK and most likely the Pulsars are OK themselves)

These tests all checked out and by themselves are probably sufficient to justify that my transistor module was bad, but I also did a couple more things. I checked that the power across the leads in 1 above was sufficient to light a 12V bulb. This was to insure that I did not have a high impedance connection in those lines. In other words a connection downstream that could give me 12 Volts but not enough to carry any usable current. I actually found this once working on a 1972 Camaro. My last double check was for the Leads at the X24 connector, Here again the above test #3 is most likely sufficient but I also found that with my voltmeter on the AC setting, I could detect a small blip on each of those three pulsars while cranking the engine, indicating that at least some signal was getting to the transistor from the pulsars.

I ended up purchasing the model and the tractor started right up. So the other piece of information is that this module can fail and knock out all cylinders. So not only is it possible it happened.
Bernie

 

[doug_cartwright]

Thanks for the feedback Bernie! It is good to know that they can all go at once. When I bought my first 322 it had both a bad transistor module and a bad hydrostatic transmission.
I Only had 1 bad cylinder,but in checking the transistor using the chart and an ohmmeter,my findings were also inconclusive.I too bit the bullet and bought the new "Magic Box". Cured.

 

[chuckv]

Bernie,

Thanks for posting the end results and the root cause of your lost spark. It is really helpful for anyone else reading this thread to see how things went.

Your approach to verify the wiring integrity, available voltage, and sufficient current at the module connectors was well thought out and thorough -- thanks for detailing your plan of attack and its results.

Glad to hear that you are back in the operator's seat...sorry to hear that you had to purchase a module but at least you were as certain as possible that it was what you needed to do prior to committing to the large expense.

Chuck