No Spark - My Riding Lawn Mower Won't start


Old 05-07-15, 07:04 PM
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No Spark - My Riding Lawn Mower Won't start

I have an old Signature TMO-31000002 (same as MTD 132A670G088) riding mower. At the end of last season it wouldn't start when I wanted to move it around in my barn. This was after a summer of flawless performance. I figured I'd fix it this spring only to find that mice had moved in over the winter. I've cleaned a bunch and even had it running one night, mysteriously, but now it won't start again. I've found that there is no spark to the (new) plugs. There is evidence of mice chewing a little on one of the wires as you can see in the picture but they don't appear to have broken the connection.
It looks like the wires connect to a block. I get how it works but I don't know what it's called and I can't find the part online anywhere.
I also see a lot of rust around the part that spins. Again, I don't know the names for these parts but I see that a good connection is needed to create the sparks in the plugs as the thing rotates.
Do I need to replace the wire/block? Where could I find it?
Should I polish the spinning thing? Should I add dialectic grease?
Thanks in advance!

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Old 05-07-15, 07:24 PM
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WoW! you gota mess going on there.
Spinning thing=Flywheel
Wire block?=Coil/Magneto

Normally any rust will not keep the system from firing unless clearance is an issue, with that said, it still would not hurt to clean things up a bit to keep corrosion from setting in.
I also do not see a wire (small wire) connected that should be your kill wire, just seems to be missing which would allow the engine to get spark regardless of any other interlocks. So Not only is that a problem, but I suspect your little friends have been busy elsewhere and caused other problems. There should be a spade terminal on the coil that a small (16/18AWG wire) attaches to. I can not locate that in the photo.
The large black wires are you high tension leads and at least the one does look to be worn through all the insulation. The other one running under the coil might also be grounding out on the block.
It largely depends on how much you are able and or willing to do as to any advice.
Also if you can find and post the model number and engine type it would be helpful.
I would begin by removing the coil via the two 1/4" headed bolts and see what is underneath.

Not sure exactly how to help more without being able to lay some hands on, some others are likely to have some ideas and surely will chime in.....
Old 05-08-15, 12:09 AM
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With all that corrosion from the mice, you may not be able to remove the coil without the bolts breaking. Disconnect the small black wire from the coil and see if you have spark. If not, your coil needs replacing, which it looks like it does anyway with the chewed up plug wires.
Old 05-08-15, 06:49 AM
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cheese, this sounds like an easy and prudent test. I'll try that this weekend.

BFHFixit, Thank you. Flywheel and Magneto. I'll remember that. I'll clean up the connections. Hope that helps. The kill wire is around on the front of the block. It's not in the picture but it is connected. I've had problems with it before.

Thanks for your insights.

Last edited by usergray; 05-08-15 at 06:53 AM. Reason: Added details
Old 05-08-15, 08:09 AM
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If you pull that magneto to clean it up, please be careful not to allow it to be scratched; the magnets are surprisingly powerful, and will want to pull that coil smack into the flywheel as soon as you loosen the mounting screws/bolts.

I cushion the distance with a piece of cardboard. I think the thickness of the cardboard used on breakfast cereal boxes is just about perfect for both cushioning, and resetting the the coil afterwards.

Some people say that two(2) thicknesses of a dollar bill is the correct air gap, or something like 0.010" to 0.012" specifically; but I like my cereal box cardboard because it's more maneuverable, especially as a cushion.

Others may have better techniques . . . . the important thing is to make sure it doesn't get scratched.
Old 05-08-15, 01:49 PM
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Vermont, thank you for the warning. You may have saved me some big troubles.

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