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Replaced coil but still not getting spark

#1

J

JohnnyMtn

I have a B&S 125cc push mower. It started stalling once it got hot and then several weeks later would not start at all. I have done lots of troubleshooting, added fresh gas, thoroughly cleaned the carb…then finally realized I was not getting a spark. I replaced the plug but am not getting a spark with the new plug.
Using a spark tester I checked the coil with the ground safety disconnected. I was not getting a spark so I concluded that the coil must be bad. So I replaced the coil with a new one, gapped it properly, but am still not getting a spark. I should mention that the flywheel does attract metal so I think the magnets are ok.
I am now at a loss as to what the problem might be. Do I understand this correctly - if I removed the ground safety from the coil and the coil is good then should a spark tester confirm spark when the flywheel is spun?
Any ideas as to what else might be causing this?


#2

H

hlw49

Did you mount the coil correctly?


#3

A

Auto Doc's

Hello JohnnyMtn,

You could have gotten a bad coil.

"New" does not mean good, especially online. Some coils have been returned many times and have traveled many thousands of miles only to be returned again and again. This is what our Amazon "free returns" society has gotten us.... lots of junk flooding the open market.

Yes, disconnecting the kill "safety" wire will allow it to produce spark, but the engine has to be spun fast enough, and the air gap needs to be correct with the coil tightly mounted. A simple paper business card is good enough for setting the air gap between the coil and the flywheel magnet.

You also need to use an open-air gap type spark tester set to 1/4 inch minimum. Simply watching the .030-inch of a spark plug gap does not stress test the coil. A good coil will produce a strong blue spark that will easily jump the 1/4 gap.

The "Christmas tree" type spark testers are a gimmick design that some fool has made a lot of money off of and they are very unreliable. Lots of misdiagnosed parts have been changed because of them.


#4

Tiger Small Engine

Tiger Small Engine

Auto Doc's said:
Hello JohnnyMtn,

You could have gotten a bad coil.

"New" does not mean good, especially online. Some coils have been returned many times and have traveled many thousands of miles only to be returned again and again. This is what our Amazon "free returns" society has gotten us.... lots of junk flooding the open market.

Yes, disconnecting the kill "safety" wire will allow it to produce spark, but the engine has to be spun fast enough, and the air gap needs to be correct with the coil tightly mounted. A simple paper business card is good enough for setting the air gap between the coil and the flywheel magnet.

You also need to use an open-air gap type spark tester set to 1/4 inch minimum. Simply watching the .030-inch of a spark plug gap does not stress test the coil. A good coil will produce a strong blue spark that will easily jump the 1/4 gap.

The "Christmas tree" type spark testers are a gimmick design that some fool has made a lot of money off of and they are very unreliable. Lots of misdiagnosed parts have been changed because of them.
Click to expand...
I have never received an obvious returned part from either Amazon or EBay, ever. I also rarely return parts. The quality of parts from Amazon and EBay over several years and hundreds of parts has been really good for my own personal experience. I hear people talking about how bad some of these parts are online. Remember, many, many parts come from China these days.


#5

StarTech

StarTech

This year a lot of the parts are not to spec off Amazon. Dampers with the wrong ends, belts poorly made, and BB aftermarket spindle pulleys the wrong height are just three of the things in the last two months that I had to get credit for and then thrown in the recycle bin. The only reason I am keeping the BB am pulleys that I can machine the .125" problem away.

I even had one vendor to claim a part to be OEM when it was obviously aftermarket as it was no where close.


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