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Briggs& Stratton Power Built 12.0 HP Model 284707

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billyho
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2018/05/12 21:38:09 (permalink)
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Briggs& Stratton Power Built 12.0 HP Model 284707

I am new here and have a problem I don't understand. I turn the key off and the motor keeps running. Put the throttle all the way down and the motor stops. I have a new key switch installed. I confirmed that there is ground continuity to the ground on the coil at all times. This wire leads from the coil to an isolated ground near the throttle linkage. I understand that pulling the throttle lever all the way down should, and does, pull the linkage to touch and connect this coil ground wire to ground. My question is, why does this wire always have continuity to ground regardless of key position or throttle position? What is stopping this engine if I always have a connection to ground at both ends of this wire? Why is it running at all with the coil ground wire always grounded? What am I not understanding? Thank you for any information you may have.

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    billyho
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    Re: Briggs& Stratton Power Built 12.0 HP Model 284707 2018/05/13 03:18:14 (permalink)
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    Going to try this tomorrow..... Check the impedance (resistance) of the secondary circuit at room temperature. Hook an ohmmeter test lead to the spark plug terminal of the high-tension lead and another to the lamination stack (ground). Your resistance reading should range between 2,500 and 5,000 ohms. If infinite (no continuity), an internal open circuit exists. Replace the coil. If infinite and the engine runs, your problem is an internal break of the high tension lead, a poor attachment of the spark plug terminal or improper mating of the high tension lead to the coil. A pin within the coil body skewers the lead. If the pin does not contact the wire core, there will be no continuity. The coil will often have enough available voltage to jump the gap, so you see spark. The internal arcing that occurs within the high-tension lead will eventually create enough resistance that ignition system performance will suffer. If your resistance reading is much lower than 2,500 ohms, an internal short exists. Replace the coil.
    AVB
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    Re: Briggs& Stratton Power Built 12.0 HP Model 284707 2018/05/13 06:17:46 (permalink)
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    Depends on what you considering continuity to ground is. These coils primary will read around 1.5 ohms between the kill terminal and ground as you reading the internal coil primary resistance. You can not test to see if the primary trigger is working which with the engine running say it is. You can't test to see it there an open circuit in the kill circuit because had the primary and electronic are setup in these coils; although if the tiny wire becomes unsoldered from the circuit board it could read open and the coil this work but will not shutdown.
     
    All you can do is to verify that kill wire when disconnect from the coil is open circuit in run position and grounded in the off position. If this is so then the coil needs replacing. Also make sure there is never any voltage applied to the kill terminal as this will destroy the coil. The secondary (high voltage side) has nothing to do with the coil not shutting down.
    billyho
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    Re: Briggs& Stratton Power Built 12.0 HP Model 284707 2018/05/13 11:38:38 (permalink)
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    Thanks so much for your input, I have tested across the coil and have no continuity. Bad coil. If it were not a bad coil, this mower should not run due to the fact I have perfect continuity to the ground wire at all times. The insulator stud is grounded and both wires to the coil and to the grounding throttle slide (hope thats the right name to call it) are together on this stud that is grounded!!!!! Need to replace the coil and I guess make sure these two wires are not grounding until the slide comes over and touches to ground. I am afraid I am missing something I dont understand. What are the chances this coil ground(Shut Off) wire is grounded all the time and should not be. At the same time the coil has failed but allows spark to travel across anyway. 
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