Runs ok--for 3 seconds


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Old 05-25-18, 12:06 PM
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Runs ok--for 3 seconds

My Stihl FS-76 string trimmer ran fine yesterday. Now suddenly it will start and run for a few seconds, then dies. Then I can immediately start it again--same story. Just a few seconds, over & over; choke or no choke. Giving it gas tends to kill it. I tried removing the fuel filter & air filter; no difference. Time to get the carb cleaned, or is there something else I should try?
 
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Old 05-25-18, 03:32 PM
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I'm sure others here have better replies, but I'd start by cleaning the gas cap. Although it generally takes longer with a larger engine, I've seen this happen with lawn mowers and such, and it only stands to reason that a vacuum in the tank is going to arise sooner with a smaller engine. If not that, I would go with a carb overhaul or replacement. I can't think which one it was a couple years ago, but a replacement carb for something I was working on was within a few bucks of a kit.
 
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Old 05-25-18, 03:37 PM
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A total replacement carb is by far the fastest easiest way to fix it.
There's so many tiny parts and orifices it's a real pain to try and rebuild one.
 
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Old 05-25-18, 05:05 PM
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Have you checked the spark plug?
Geo
 
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Old 05-25-18, 08:35 PM
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I agree with just replacing the carb. They are so cheap these days that it isn't worth trying to rebuild it and possibly end up having to replace it anyway.
 
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Old 05-27-18, 12:30 PM
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Wow--Just for the heck of it, before replacing the carb, I cleaned it w/ spray carb cleaner. That miraculously cured it! (this time...)
 
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Old 05-27-18, 12:37 PM
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Hi, run some Seafoam through it to clean the whole fuel system out.
Geo
 
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Old 05-27-18, 01:12 PM
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I had tried some other carb cleaner of the type you dump in the tank; then repeatedly, about 30 times, started it; waited for it to die after a few seconds; started it again...

The carb cleaner that you spray into the carb worked a whole lot better. But did not try Seafoam. Does it seem to be better than other carb cleaners that you mix w/ the gas?
 
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Old 05-27-18, 02:49 PM
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I have had good luck with it, it’s a bit expensive but have you to loose?
Geo
 
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Old 05-27-18, 03:05 PM
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Seafoam does not nor claim to do anything for diaphragm carburetor's. It will not rejuvenate diaphragms and gaskets.
As already mentioned I agree to replace the carb and fuel lines.
 
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Old 05-27-18, 05:39 PM
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Taking off the carb and cleaning thoroughly should cure the problem and order a rebuild kit and replace your rubber parts and gasket every season. I'm betting your using 10% ethanol fuel. What happens is when the trimmer cools down and condensation forms (no matter how little), the ethanol separates from the gas and binds to the water molecules and forms a varnish. This is why gas won't keep for more than a couple of months anymore, especially in a garage or storage shed where temperatures fluctuate quite a bit. To help combat the problem of crappy gas, get yourself a 2 quart mixing cup and use a MixMizer and only mix a 1/2 pint to a pint at a time.
 
 

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