Diagnostics for ignition problems?

[jteneyck]

I have a Shindaiwa 345 that I got cheap that I thought I would use for spare parts for another that I have.  The one I have keeps running and running, and the one I got cheap looks in pretty good shape except it has no spark.  There are three major parts to the ignition on these saws, an exciter coil, a pulser coil, and an ignition coil.  The exciter and pulser coils both take input from the flywheel.  I had a spare exciter coil so I put it on, but still no spark.  The 345 is known to have failures of the ignition coil, and they are no longer available from Shindaiwa, or anywhere else that I've been able to find.  But my question is is there a way to diagnose which coil really is bad?  Is there some kind of voltage, continuity, etc. test that will pinpoint where the problem is?  Assuming it really is the ignition coil, could some other ignition coil from another manufacturer work be substituted in order to get it to run?  If so, how would you determine which one?  Thanks in advance for your help. 

[bill m]

Have you checked the  kill switch to make sure that is not the problem?

[jteneyck]

Yes, the kill switch is good. 

[Al_Smith]

They like to keep the theory of solid state ignitons under lock and key,big secret you know .

Taking a wild stab at it ,in by pea sized mind I would assume by the discription that the exiter coil is the low voltage section ,the pulser the solid state switching device and the ignition coil the high voltage section .

Now if my huncjh is correct then the exiter and ignition coils are merely the same as an auto transformer having one side of each respective coil connected to a common ground .If that is correct then you should be able to do a continuity test to check for opens or grounds . How one would check the switching device I haven't a clue .

[jteneyck]

Al, I would say you are correct with respect to the function of each coil.  I tried some continuity checks earlier, with no info. gained.  I plan to pull apart my good saw enough to do some comparative continuity tests between it and the dead one.  Thanks for the input. 

Any ideas on how to go about finding a replacement (none OE) ignition coil if it turns out to be bad? 

[Kevin]

https://forestryforum.com/board/index.php/topic,42621.msg615640/topicseen.html#msg615640

[joe_indi]

Shindaiwa is one of those companies that still plays spoilsport by having separate components in the ignition system.
You could try the components from some other Shindaiwa model.
Optimistically, component part number might be different for some other model just because of a different length of a wire or placement of mounting hole.
Unless you actually see the components  of another model, you would never know whether they can be used as a replacement.
Part numbers might not tell you this.
Most service people will not usually go that extra yard to help you in this aspect.
Here, we have the time and patience to do something like I have described, and I might get a person carry some saw's part all the way from an island 500km away, to find out whether I could get him a suitable substitute.
This is no joke. I actually had some a guy walk into my shop asking for a ring (not 2 just one) for an Echo saw.He had just this one ring with him as a sample.
If you look at a map for Lakshadweep on the west coast of India you will understand the trouble this guy took to come all the way here with that ring.
Since I  nor anybody else around stocks Echo parts, I gave him some of the old rings that I had and advised him to file one of the more suitable ones to fix his saw.
He must have been successful because he has not returned for more rings.

[Al_Smith]

Ignition retrofits have been done in the past but it's a guessing game as to what might fit what .The problem is both the coil lamentaion spacing plus the mounting provisions .

MacBob somehow got a Japanese solid state weedwacker coil to work on a Mac 125 . My guess is it took a little bit of thinking to come up with that fix .

What a guy needs to do is find a friendly small engine shop with a pile of old saws and weed wackers out back that is about a semi load of junk that they will let you take apart . Kind of like the proverbial needle in the hay stack .

[jteneyck]

I tried various continuity, resistance, and voltage checks on the three major components, but didn't learn anything of value.  To do that I had to pull apart the connectors from each.  Some of them were pretty much drenched in chain lube.  I don't know if that is typical of all saws, but I cleaned all the connectors before putting them back together and, what do you know, I had a spark!  Hard to believe that was the problem, but that's all I did.  I bought this saw used - well used by the looks of it.  So after I had a spark, I opened up the carb and found the screen all covered in saw dust.  I cleaned out everything, put a carb rebuild kit in, bought a new fuel line, and it started right up and runs great.  The rings looked a little worn when I had the muffler off, but it runs pretty strong, so I'll leave well enough alone until they need replacing.  Got lucky on this one.  Thanks for your help and advise.  Glad I didn't have to go down the replacement path after all. 

[Al_Smith]

I can't honestly say that I've ever seen that model of saw and certainly have never worked on one .However as with most ignition systems more times than not the problem will be on the low voltage portion of the circuit .This would explain possible high resistance between the coils due to oils etc. accumulating on them and thusly causing low or no current flow .. Glad every thing worked out for you . 8)

[jteneyck]

So I was using my "new" saw today.  Started right up and ran great for about 15 minutes, then just quit, no sputter, nothing but silence.  Pulled it over a few times and it wouldn't even cough.  So I'm thinking no spark.  I pull the plug - spark.  I put the plug back in - nothing.  Pull the plug again - NO spark.  Huhh?   ???  I looked at the plug wire end, and it looked OK but I squeezed it a little and pressed it firmly onto the plug - sure enough, spark.  Put it back together and it's running fine again. 

So maybe the root cause of the electrical problems really was just the connection to the spark plug.  Kind of makes more sense than oil in the wiring connectors.  Also something to keep in mind if your saw looses spark. 

[sablatnic]

Or you might have a hole in the wire letting the electricity out.    ;)