Troubleshooting trimmer engine

broo

Member
Joined
May 18, 2018
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4
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I have a Troy Bilt TB80 trimmer that turned 9 years old this year.

Worked fine for the first few sessions of the year, then the engine started running poorly, as if it "missed" a spark sometimes.

The engine starts and idles fine, but under load, even light load, it seems to miss every second or so, sometimes long enough to stall the engine.

Fuel should be fine, as it's the same 40:1 mix I use in my chainsaw which runs good. The mix was made about 2 months ago and I always add fuel stabilizer as I never know how long it'll take me to deplete that single gallon can.

Air filter is fine. I tried running it without an air filter (not doing any actual work though), and it still misses.

I checked the spark plug, which seemed good, but since I had a spare I changed it, making sure the gap is the specified 0.025". No progress.

That's about all I can think of. I don't have much mechanical knowledge except the very basic stuff I listed here.

Is there something else I can do or should I bring it to a repair shop ?
 

Romore

Well-Known Member
Joined
Jan 19, 2019
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1
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258
Try disconnecting the switch, it may be making an intermittent ground. Otherwise I would suspect the module. Shop time will cost more than a new trimmer is worth, after 9 years it doesn't owe you anything.
 

broo

Member
Joined
May 18, 2018
Threads
4
Messages
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The switch didn't help, so I went to a local parts store for the module. He had a very similar part, exact same shape, but the spark plug wire is 1" longer. Bought it for CAN $20. I replaced it and now it works great.

Thanks for the module suggestion Romore :)
 
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