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Hey everyone, I'm hoping to find a solution to my snowblower problem as it is pretty much useless right now. I have a Craftsman model# 536.885471 snowblower that I bought used. It starts up perfectly fine and even runs/makes a few passes in the driveway. The problem is that after about 15-20 minutes it starts to run rough/won't work if the auger is activated. I've done a lot of searching and tried loosening the gas cap, but it doesn't help so I don't think that the cap is faulty. Next would probably be the carburetor clean/replace or the coil. The person I bought it from said that he replaced the carburetor however, and like I said it runs fine but dies after a while. Anyone have any instructions/part numbers for the carburetor/coil replacement? Machine works really well otherwise, just has to keep running :icon-doh:. Also, I have premium gas in there now, how long is gas still considered "fresh". Any and all help is greatly appreciated! TIA!.
 

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Bring a known good spark plug with you and run it until it dies. Immediately pull the plug boot and stick the good plug on, ground against the head and look for spark. If you see none, or very weak, your coil is going south. If you still have strong spark your valve lash is next suspect. 15-20 minutes run time I wouldn't consider the carb, especially if you've ruled out the fuel cap.
 

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Thanks for the quick response! Should I just pick up a new spark plug from the autoparts store and try that? Maybe I should just swap out the coil for a new one if it isn't too involved/expensive? Could stale gas cause this as well? Like I said it runs fine with the gas that is in there, but just doesn't stay running.
 

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Realistically, you can use any spark plug for the check, but a similar one is fine. If you get a direct replacement, try it in the machine and use the other (old) for a check if it dies. You could get really lucky and it just be the plug, but not likely given your run time. The coil is a simple replacement, but involves removing the recoil shroud which some folks find daunting, but it's very simple.
 

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Google testing mower ignition coils for testing. You need a multimeter. Doubt if it's the spark plug. I'd first drain the fuel bowl, maybe water, maybe the petcock is not opening. Eliminate those then it's the carburetor.
 

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Get a compression tester and check compression when it's cold using the electric start. Then check it again when it warms up and has no power. If you see a significant difference, you likely have exhaust valve clearance issues. As the engine warms up the clearance decreases and the valve doesn't close. It's an easy fix if you have some mechanical aptitude.
 

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Today's Gas goes bad quick. Ethanol Compatible Fuel Stabilizer is a must for all small engines, that goes double for Snow Blowers, which run in a Water Vapor enviorment . Drain the Carb Bowl, and look for water [ little balls ] or black specs [ fuel line failing ] . Oftentimes, dirt / water settles to bottom of Carb Fuel Bowl, and needs a few minutes to loosen up, and plug carb jet. Afterwords, it sinks back to bottom of bowl, and machine starts right up, only to stall out later .
 

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Snows, I'm in the Dave camp. Start with compression testing first. If the internals are not performing, throwing money and parts will not make up for low compression. It wastes time and pisses of the owner. Even with compression release, the gauge should hit a strong 40psi on 1 engine revolution, and much higher without compression release. Test, Don't Guess. GLuck, Jay
 

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All posts excellent advice, based on years of experiences. As a summer job you might want to get a modular ignition controller. They work great, and are easy to install. Post when you solve this problem.
 
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