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Weak spark


Jack B.'s Avatar
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06-19-04, 02:23 AM   #1  
Weak spark

I have an MTD w/b mower with a Briggs engine. If I put a spark tester from HV lead to ground I get about 1/4" spark. However, I can remove the spark plug, put the plug wire back on it and ground the spark plug...I only get a very minute spark. I tried this with several spark plugs...same result. It won,t start...but runs for a few seconds with starting fluid. I was going to rebuild the carburetor and redo the valves but do you think this weak spark is part of the problem.

 
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Azis's Avatar
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06-19-04, 11:30 AM   #2  
Azis
If it will start and run at all most likely the problem is not spark related. Try putting a few drops of raw gas in the carb and see if it runs for a few seconds, (starting fluid can be hard on small engines as it burns pretty hot) if it does and you want further convincing that it is fuel related, put a few drops more than thr first time and see if it runs a second or few longer. This should verify if you have a fuel problem.
If so then start with the easy stuff, pull the fuel line at the carb and check for fuel, if not then check fuel filter lines tank and tank vent, if yes then a good carb cleaning and or kit should get ya goin.

 
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06-19-04, 11:26 PM   #3  
I agree, it does sound like you have sufficient spark. The spark will only be as long as the width of the gap in the plug (.030"). Not sure which engine you have, but by your description, I'm betting you have a 5hp or larger with a bowl type carburetor. If so, remove the bowl, clean it out, and clean the tiny hole in the bowl screw.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
Jack B.'s Avatar
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06-20-04, 10:52 AM   #4  
Thanks Azis and Cheese for your replys. It's a pretty old machine so I think I'm going to rebuild the carburetor and reseat the valves. The only thing I was worried about, was that I'm used to getting a fat blue spark...with this one I'm getting a very weak spark (even tried it with several new plugs).

 
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06-21-04, 12:17 AM   #5  
I don't know how old it is, but if it has points and a condenser, I would replace them anyway, just to be sure. But if it is sparking well enough to run, then it's probably ok. Try it with the gas instead of starting fluid just to be sure.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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