Craftsman Trimmer starts then dies

gopack03June 15, 2009

I have a 2 year old craftsman string trimmer (model number 316.791810) that starts up for about 2 seconds to 1 minute and then dies. It didn't work when I pulled it out of the garage this spring so I rebuilt the carb and it worked fine for about a month until it started to idle really hard and became harder and harder to start until finally it wouldn't start at all. When it does start up for a second or two it runs extremely rough. I have cleaned the carb again, re-adjusted the carb pin, replaced the spark plug, put in fresh fuel, checked the fuel lines, adjusted the idle screw, adjusted the carb mix screws, cleaned the air filter and muffler filter, and even cleaned the fuel cap vent. I have no clue what's going on, I think that it may be getting too much or too little fuel. Please help!!!

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petzold6596(8b southern NM)

Check the cleanliness of the fuel tank.

    Bookmark   June 15, 2009 at 10:32PM
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chinquapin

If you let set for any length of time with old gas and no
stabilizer, you could have varnish build up in carb. It's
very hard to get out even with a good carb cleaning.
If the carb has a primer bulb, you may have a leak in fuel
line or primer bulb. Had similar problem with a Ryobi and
it was one of the lines to primer cracked. After putting on
new lines the primer bulb cracked. With new bulb and lines
it runs fine.

    Bookmark   June 16, 2009 at 2:09AM
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gopack03

Tank looks clean. Is there a specific way to clean it out? Checked the fuel lines, they looked fine. Is there some sort of test that you can do to make sure they are not cracked? There is a priming bulb but not one connected to the carb. I don't think that the carb is dirty because I ran it for about a month before it died. I did mess with the adjustment screws on the carb though but then i put them both back at 1 1/4 turns out from set, could that do anything? What about the idle screw, I messed with it a little bit as well.

    Bookmark   June 16, 2009 at 3:07AM
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baymee(LehighValleyPA)

Sometimes the diaphragm is worn out. If it has a spark arrestor screen, it could be plugged. Heat with a torch and let it cool, knock off the dust.

    Bookmark   June 16, 2009 at 11:15AM
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gopack03

Cleaned the arrestor screen, looks brand new. Also, I just replaced the diaphragm in the carb when I rebuilt it a month ago. Still no luck.... P.S. It seems to run better with a dry spark plug and no choke or priming... if that helps at all.

    Bookmark   June 16, 2009 at 12:46PM
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masiman(z7 VA)

You can test the engine for leaks but it requires a pressure/vacuum tester. It is not difficult to do but can take some time with disassembly and setup.

I recently had to do it to a chainsaw of mine. Same symptoms, would start normally, but die within a minute or two. I thought my seals were leaking. It turns out my spark plug and decompression valve were leaking. Replaced both and saw runs fine. Way cheaper and less hassle than blindly replacing seals.

Decent small engine faq

Leakdown, Pressure and Vacuum testing

    Bookmark   June 16, 2009 at 3:16PM
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