311777 0164 15 HP B&S burning up ignition coils

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GreatScott59

Forum Newbie
I have replaced the ignition coil 3 times, 4 timess counting today. They would last 6 to 8 weeks. The last one lasted a whopping 30 seconds and died. I just replaced the head gasket and related gaskets, cleaned the carbon off the head and valves. Was running like a top after the repairs were made. Then poof, engine died. Then bought a new coil this morning and now shrugging my shoulders. Voltage regulator? I am clueless.
 
I’m assuming you are using OEM coils #591459. This is one I’ve only seen once before. That time the customer had a bad ignition switch which applied voltage to the magneto terminal burning up the coil. I would test the switch to may sure yours is not shorting to the coil.
 
B&S OEM 595304. The lawn mower shop did not have the 591459 in stock and said this one will work. Of course they told me no returns on electrical parts. When you sit the 2 side by side, the coil on the 591459 was larger. How does the short in the electrical switch explain the previous ones lasting 4-6 weeks? Luck? LOL
 
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If set up properly so it is not touching the magnets as they pass, only 2 things cause coils to fail
1) too much resistance at the spark plug ( which is why you ground the plug when spinning the engine )
2) Voltage being applied to the kill wire which fries the Hall Effect trigger chip embedded in the magneto .
The latter are very sensitive and the tiniest amount of voltage can fry them, a lot of cheap digital meters can in fact destroy them .
So some where in the wiring system the kill wire is getting voltage
Corrosion inside a key switch for instance can do it
Corrosion in a combined brake or PTO switch can do it
A bad voltage regulator can do it.

All of these are MOWER specific to engine specific so we need the make model & serial of whatever the engine is in.
FWIW I had a mower come in that had been retrofitted with a battery start engine & the power return from the alternator made occasional short to the bracket the mechanical kill wire was connected to .
 
And I have seen faulty ignition switches that randomly sends a monetary voltage along the kill wire. The customer lost two coils and I lost one before I found the switch problem. I even had one switch that sending just 1.5 volts along the kill wire that was blowing the coils and this was a new switch.
 
IF you doubt what you have been told about the switch, disconnect the "Kill Wire" from it and see what happens. The Kill Wire will have to be kept from touching anything until you are ready to shut the engine off then just ground it.
Walt Conner
 
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