Craftsman Leaf Blower - Dies when hot

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  #1  
Old 10-21-12, 10:05 AM
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Craftsman Leaf Blower - Dies when hot

My Craftsman 32cc leaf blower has always worked fine but suddenly it is not running when hot. It starts fine and runs well for about 15 minutes or so, then it bogs down. If I let off the throttle, it will idle but if I don't let off, it will stall. If I let it idle for a minute, it will rev up again, but will soon bog down.

I found that the fuel line had deteriorated and replaced it. I could blow easily through the fuel filter. This had no effect on behavior, though. I tore it all down and de-carboned the combustion chamber and piston. I cleaned the rings. No effect on performance. Tried different spark plug, no change. I have not taken the carb apart and I have never touched the settings on it.

Any help out there? Is this a fuel problem? Could the ignition system be shot and breaking down when hot?

I should mention that the blower is 20 years old. Yes I know that's a good life, but I hate throwing out stuff that can be economically fixed.

Thanks for any help you can offer.

Gary
 
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Old 10-21-12, 02:13 PM
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If you had a bad coil dying when it got hot it often is more like turning it off like a switch, so I think you have a cooling or fuel related problem. When it tries to die the next time unscrew the fuel cap a bit to vent the tank. If it runs fine you have a bad gas cap.
 
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Old 10-21-12, 03:20 PM
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Thank you for your suggestions.
I did two things - I took the fuel filter out and cleaned in in alcohol to make sure it wasn't clogged. Blew it out with can-of-air. I also took the cap apart to make sure it was passing air and to make sure it, too, was clean. If I fill the cap with alcohol it will drip out slowly. I blew it clear also.

Tried the blower again. No change in operation - it works fine until hot (about 5 minutes at most), then bogs down. Sometimes I can goose it back for a few seconds.

(Added) I even tried running it with the cap off and the filter removed to make sure these weren't the culprit.

I used fresh gas (same as I use for lawn tractor) and the same 2-stroke oil I have been using for years (I bought a case of one shot bottles years ago and have never had a problem with it).

Could the 2 stroke oil have gone bad over the years though it is in individual sealed bottles?

I really need to get this resolved - leaves are piling up!!
 

Last edited by GaryK227; 10-21-12 at 03:27 PM. Reason: Left stuff out
  #4  
Old 10-21-12, 06:11 PM
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Sounds a lot like you may have low compression. Try dribbling a bit of oil into the spark plug hole after it dies and see if it will start back up and run good momentarily. Also sounds like it could have carb probems or an air leak.
 
  #5  
Old 10-21-12, 07:38 PM
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When it dies, it does start right up again and runs well for like 10 seconds or so then bogs down again. That's without dribbling any oil in the cylinder.

Nothing had ever been touched before on this blower and everything was tight when I took it apart.
 
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Old 10-23-12, 03:48 PM
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Today I thought to dismantal the carb and see if anything was clogging it. I found some gunk in an area in front of what looks like a screen. Cleaned it out, blew all the passages clean with brake cleaner and air, re-assembled. Still had same problem - runs for a few minutes, then bogs down. I closed the choke a bit and it ran fine. After a while I opened the choke entirely and it kept running at full throttle until I brought it down to idle and tried to open her up again, but a slight closing of the choke (about 1/8) and it runs fine.

So, I guess this point to an air leak? I assume the gasket under the carb? Or can something else cause this? I guess I can continue to run it this way, but I would rather fix the problem.
 
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Old 10-24-12, 01:14 AM
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Well, an air leak could be at a number of places, from the intake area to the crankcase gasket or the crankshaft seal. Spray some carb cleaner around these areas and see if the engine revs very noticeably. If so, that's the area. You could also have a problem with the metering or fuel pump diaphragm in the carb or the pulse that drives the fuel pump.
 
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Old 10-24-12, 10:41 PM
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Thanks for your response. I will see what I can do about the air leak tomorrow, but I have to remove the covers. Do I use the carb cleaner while the engine is idling or at full throttle?

The other items you mentioned -
the metering or fuel pump diaphragm in the carb or the pulse that drives the fuel pump

I assume are all part of the carburetor. Would a carb rebuild kit cure them? I dismantaled the carb and all looked OK - mone of the diaphrams were torn or cracked.
 
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Old 10-24-12, 10:50 PM
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Do the carb cleaner at either idle or full speed if full speed is less than it should be.

The diaphragms are part of a rebuild kit, but a new carb is cheap. The diaphragms can be bad without being torn or cracked. If they are too stiff or leaking they will not work right.
 
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