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i have an older bolens bl250 trimmer that i'm cleaning up, and i'm stuck on one problem. it runs strong, but the kill switch doesn't kill the engine. based on how it's wired, it appears that the switch is supposed to ground the coil/magneto, removing spark from the spark plug. well, the switch works, the wiring to and from the switch is good (all checked with a meter)...but the switch won't stop the engine. i either choke it or pop the plug wire off.

any ideas about how to get this kill switch working?

thanks in advance!

dan

The problem could be in the coil itself if all wiring and switch are working properly. You can test the coil by removing the small wire going to it and hooking up a test lead which you can manually hook to ground. If you have to disassemble the trimmer to the point that is not able to start, just pull the spark plug and leave it connected the the coil wire. Pull the starter rope and check for spark, then ground your test lead and pull the engine over again and see if spark is present. If spark is present with your known-good test lead grounded then the coil has an open somewhere in that circuit and you will need to replace the coil or get a grounding strap like we used to use on the old Briggs engines where you ground the secondary side at the spark plug itself. You can always do what you have been doing and choke the engine to kill it, too.

If you put an ohm meter across the switch and checked the kill wire(s) for an open and everything tested good than all I can think of is the coil itself.

Let us know what ultimately fixes your trimmer.

I forgot to add that you may have to hook a test lead with two alligator clips, one clip to the side electrode of the spark plug and the other to an engine ground to be able to watch for spark while you pull the starter rope.

Thanks for the diagnostic advice. I bypassed the switch and directly grounded the coil, but still runs like a champ. Coil is available online, but for ~$55. I doubt this machine is worth that much.

Can you explain the ground strap solution in more detail? Maybe that would be a more economical approach for me.

Thanks!!

Dan

tacod said:

Thanks for the diagnostic advice. I bypassed the switch and directly grounded the coil, but still runs like a champ. Coil is available online, but for ~$55. I doubt this machine is worth that much.

Can you explain the ground strap solution in more detail? Maybe that would be a more economical approach for me.

Thanks!!

Dan

Click to expand...

Back in the day we had mini bikes and the only way to kill the engine was to use an ignition shorting clip that was bolted to one of the head bolts and when you bend it toward the spark plug boot the point on the clip would penetrate the spark plug boot and touch the spark plug lead which would ground the coil and kill the engine.

Here is a link to what I'm talking about: Ignition Shorting Clip For Briggs & Stratton 220197, 225171, 690578

The price is good for one clip but the shipping is crazy. Check with your local lawn mower shop. I don't know how you would bolt this particular clip to a metal part of the engine but if you are resourceful you can probably make something that would work just as well.