# B&S Coil Grounded



## RKDOC (Jun 20, 2006)

This is on a B&S 422707-1232-01 Code 90120132. This is on a Murray Riding mower. The customer brought it in with some other problems. He said he has not been able to shut the engine off with the key for quite a while, so to check that also. In checking the wiring I found that the terminal on the coil where the kill wire attaches, is always shows continuity to ground. Is this right? I should have to have the kill wire go to ground to kill the engine. The engine runs great just won't shut off with the key. Is this opposed engine wired different? or do I have a bad coil?Seems strange to me. Thanks for the help.


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## duffer72 (Jul 23, 2011)

Does it show continuity all the time no matter what the key position is? where does the other end of the wire go to, has someone run it to the throttle plate so it will only shut off with the throttle. How does he shut it off? That coil isn't wired any different than normal. just for my knowledge are any of "the other problems " electrical in nature? 

I will be interested in what you find as I never seen that in 40yrs other than a bad key switch but that wouldn't explain the constant ground.


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## RKDOC (Jun 20, 2006)

I am checking the continuity at the little tab on the coil where the kill wire hooks up. The wire is not connected at this point. I was tracing wires to see if I could find why the key did not turn the mower off. Every where I checked I had continuity to ground (with key on). How does the engine start if the coil is grounded? Mystery to me. Thanks


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## 30yearTech (Sep 14, 2006)

If your just testing for continuity to ground, you will get a complete circuit when you check the kill tab on the side of the coil. A coil after all is just a coil of wire and the wire inside will complete the circuit. 

Have you tried grounding the kill circuit manually to test and see if that would kill the spark? Try bypassing everything and short the kill lead to the engine block, I bet you will find that this works to kill the engine.

Check for good electrical ground between the engine and tractor frame, and between the switch and frame. I find that most times it's either the switch or just a bad ground connection.


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## duffer72 (Jul 23, 2011)

30yr you may be right on the ground, I have never checked one that way to be honest, usually disconnected the kill wire and cranked it, no spark new coil.


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## 30yearTech (Sep 14, 2006)

duffer72 said:


> 30yr you may be right on the ground, I have never checked one that way to be honest, usually disconnected the kill wire and cranked it, no spark new coil.


I know they will read continuity to ground, as I used to look for shorts in old point/condenser ignitions with a continuity light. If you did not disconnect the coil ground you would always show continuity through the circuit. With the ground disconnected you could easily tell if the points were making contact, if a condenser was shorted to ground, or if any of the lead wires were grounding out. The only difference with a solid state unit, is that they have a solid state trigger built into the coil to replace the breaker points. The coil portion is basically the same as they were when they used points 30 years ago.


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## RKDOC (Jun 20, 2006)

Thanks for the help, and the lesson on coils. I never had checked a coil that way. I just thought if the kill lead showed it was grounded, the coil would not work. Still can't find a problem with this system , but a new wire from key to coil solved the problem. Thanks for all the help.


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## duffer72 (Jul 23, 2011)

Now that you mention it, I remember checking coils for hotter ones when I was building racing go kart 5HP briggs engines in the early 90's, would check ohm resistance from the spark plug lead to the metal base of the coil, a good coil was about 3500-3800 ohms anything lower would go in stock for lawnmowers, used to get 1 or 2 out out 10 that were keepers.


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