Author Topic: baffled by no spark condition on Poulan 3300/Craftsman 358.356330. Coil resistance values?  (Read 157 times)

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Offline hillpc

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Running fine last week, died (think I ran out of gas), refilled, never started again.  No hint of a spark across new (or old) plug, out of the cylinder head, grounded to metal, with kill switch wire completely disconnected.  Armature/flywheel magnet air gap tried at 0.010" and 0.014"  This ignition system is simple, just flywheel magnets, armature/coil, plug wire, and plug.  Several websites said if it doesn't spark, the armature/coil is bad.  530 039128 coil no longer available new, so I bought a used one from Chainsawr.  That one doesn't spark the plug either.  The plug will spark hooked up to my car ignition, and a known good car spark plug will not spark on the chainsaw coil.  I used a cordless drill to spin the flywheel to make sure it was going fast enough to allow a good spark.  I used the first two testing for spark instructions at https://store.chainsawr.com/blogs/tuning-and-repairs/1125992-how-to-test-a-chainsaw-ignition-for-spark (spark the plug in air, check for pulses), but not the 3rd one that says hold the plug in your hand and see if you get shocked.  :o The second method puts a DC voltmeter on the 20 volt scale and looks for pulses to the spark plug boot.  I get those, but no spark on an actual plug, so it's trying to do something but it must be too weak.  Obviously 20 volts is not enough to jump a spark gap, so I wonder why the test specifies that voltmeter range. 

So I measured the resistance of the old and replacement coils; both exactly the same at 7.3 kohm secondary from ground lead to spark plug boot terminal, and 1.3 ohms primary from kill terminal to ground lead.  (The coils have a ground wire lead coming out that is bolted to metal, in addition to the kill terminal.)  Anyone know if these numbers seem correct?  Both bad coils?

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Offline Al Smith

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This happened .On an Echo weed wacker I lost the spark,new coil, still no spark .One magnet in the flywheel had  lost part of it's magnetism .I stroked that magnet with a rare earth powerful magnet and restored it .However after sitting over the winter it again lost magnetism .You can kind of test of the magnets with a small screwdriver by seeing how much pull they have .
The power a magneto puts outs depends on the strength  of the magnets and the relative  speed they rotate passed the laminations of the coil .My father had an old Husky garden tractor that never had any spark after sitting over the winter .He wound it up with the engine from a reel type mower  at full throttle,3600 RPM .It started and did so the rest of the summer .Now weather that restored some of the magnetism or he scared the old engine  to death I'll never know but it worked .Come or bleed you rascal --- ;D
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Offline hillpc

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Unbelievable.  I stroked the flywheel magnets with another magnet, and the saw fired up.  I've seen it written and been told that the magnets never go bad, though I have seen it written that a whack to a magnet can make it lose its magnetism.  Go figure.

Thank you.
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