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Ignition module testing

Started by bandmiller2, April 23, 2009, 01:45:55 PM

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bandmiller2

Have any of you brighter fellas figured out how to test the modules out of the saw with common meters.Theirs not much to them just a couple of leads and the grounded core??Frank C.
A man armed with common sense is packing a big piece

Al_Smith

 In answer,no.There is more to them than just a laminated iron core with some windings .The thing contains a few diodes of one form or another plus a capacitor or two .

Hilltop366

I'm not sure if I fall in the "brighter" slot but I will say this.

Back in the 80's - 90's when I worked on mostly motorcycles and ATVs the maker would supply specs for ohms to the connectors for the CDI, could be my meter was not good enough but often they would test good and not be, or test no good out of the box and work fine.
The only good test was to switch with a known good one.

As far as the coil part of the picture the ohm spec was more reliable and a dead short to ground or open was easy to see on both the primary and secondary.

Because they were seperate if the problem was not seen (making sure to try all the safty and kill switches) the coil was usually changed first (way cheaper to buy). The factory test were not very reliable.

joe_indi

Try using a digital tach.
That is what I found the best for spot checks on the module.
The tach is designed to show rpms, which are current pulses strong enough to produce a spark.
Remove the spark plug, hold the tach near the spark plug lead and pull the recoil starter.
If you get a reading the module is producing sparks.
Slow pulls give you a reading of 80, 100 - 120.
Brisk pulls show 120 - 180 or even above 220 rpm.
If you get these the module isproducing enough current to produce a spark.
Further checks could then move on to the spark plug, kill switch wire, spark plug boot etc.
But...
Whether the module is producing the spark at the correct is something to be checked.
For that more 'exotic' tools might be required.But the simplest such tool was the cheap xenon timing guns which needed no direct connection to the ignition system.They were powered by a 12volt battery.The triggering was by a loose clip around any spot on the ignition lead.
Some bright chalk was required to mark the flywheel and base and you were ready.
Joe

bandmiller2

Thanks guys,guess if the saw runs thats the best test.Frank C.
A man armed with common sense is packing a big piece

joe_indi

Quote from: bandmiller2 on April 24, 2009, 07:16:21 AM
Thanks guys,guess if the saw runs thats the best test.Frank C.
No frank,
Before trying to start the saw, after you check the saw for 'probably working electricals',
flood the engine a bit with the spark plug removed.
Clear the flooding by pulling on the starter a couple of times.
Fit the plug and try starting now.
Nowif the saw starts and runs, that's the best test
Joe

Al_Smith

Generally speaking they either work or they don't .

The one exception to that rule I have found pertains to the SEM self advancing coil used on the 042-048 Stihls . They can work find ,the saw starts just dandy but cuts out at about half throttle . This I might add is enough to drive you nuts trying to figure out or at least it did me . Then too I might be closer to the edge than most,debatable . :D

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