# Low or no Spark



## jack13man (Apr 28, 2008)

Need your help again.....I am trying to help a friend with his mower.....JD with a 20 hp Briggs. It would run fine for a while then start missing and die on him. He could leave it set....sometimes for an hour ...sometimes until the next day when it would start back up for him. Sometimes he could cut a couple of hours...sometimes only 15 minutes or so. 

When it dies it has no spark or a faint intermittent spark on both plugs. (using a tester) When it is running the spark looks much stronger. 

I suspected an ignition module or something to that effect but I would think it was odd if both went at once. Is there something else that would control the spark to both sides?

Any suggestions on what to check or look for would be appreciated. 

441577
0113E1

Thanks for anything you can do to get us started with this.
Jack


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## chuck_thehammer (Oct 24, 2007)

I would check the safety switches first and the ign switch. intermittent or poor connection.


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## 30yearTech (Sep 14, 2006)

Sometimes spark is hard to see, especially in bright sunlight. You may want to check the wiring harness that attaches to the ignition modules. There is a diode assembly in them to prevent feedback to each coil. The diode may be failing causing an issue.


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## jack13man (Apr 28, 2008)

Thanks for the quick feedback......I will start checking tonight......BTW....we were checking for spark last evening just before dark. Not sure how to check the diode but I will try to educate myself on it.


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## justin3 (Apr 10, 2007)

A Diode is basically an electrical one way valve, it will allow current to flow in one direction, but not the other.


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## small engine (Oct 14, 2010)

Your can check if the diode is working with a meter, put the hot on one side and the negative on the other, then switch the hot the the negative if it only shows flow one way its working, but that probally wouldnt tell you the problem since you said it happens after you mower after awhile, its also possible that the coils are bad, bec i have hear sometimes when the coils are bad when everythey get hot they will shut down


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## mc_harley (Dec 12, 2009)

It could be an easy problem. I had it twice on a Briggs and Stratton. The stop wire goes behind the starter to the ignition. When the starter is fix to hard it might squeeze this stop wire and that could cause a short-circuit to ground. Than the Briggs and Stratton can start or won't because the wire doesn't always make a short-circuit. Try to make the wire go free behind the starter and check the wire for damage.
Mc_harley


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