Craftsman Tractor Doesn't Shut Off Immediately

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mez

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My lawn tractor engine doesn't shut off immediately. It sputter and then shut off. Any ideas?
 
Two things happen in most recent tractors when you turn the key off:

1. The ignition circuit is grounded, stopping spark.
2. The fuel solenoid on the carb closes, stopping fuel.

I'd be looking at #1.
 
Yes. It recently been hard to start and when i engage the blade it sometimes dies. Now it doesn't shut off immediately.
 
Could be dieseling. Wonder if it's running lean, this can lead to both dieseling and the hard starting.
 
I assume it's dieseling?

make sure the spark plugs are the correct ones
the idle speed may be too high
the idle mixture may be incorrect
it may have excessive carbon in the combustion chambers


As mentioned above, you need to return to idle for a minute or two before shutting down. I don't know if it is new enough to have a fuel solenoid. As stated above, make sure the ignition is getting shut off. Your Owners Manual should have a wiring diagram.
 
Lean carb and/or hot spots in the combustion chamber igniting fuel without needing the spark plugs sparking. Try choking the engine when you shut it down and see if that makes it stop quickly, that will enrich the mixture at shutdown and should keep it from dieseling because of a lean condition.
 
Usually happens when the engine is running too hot. Take off any engine cowlings and shrouds that you can and blow off the leaves and debris from around the cooling fins. Could have a mouse nest under the engine cover.

Also, if the wrong heat range spark plug is installed, dieseling could occur. Change the plug out for a factory plug (Champion RC12YC most likely)

Other possibles are a lean carburetor issue caused by a clogged main jet. Would need to rebuild/replace the carburetor.

And lastly, I would check the valve clearances to make sure they are spot on.
 
Originally Posted By: mez
My lawn tractor engine doesn't shut off immediately. It sputter and then shut off. Any ideas?


Is this a newer machine?

I've experienced this phenomena with several late model, single cylinder and V-twin equipped riding mowers. Most notably was my Cub Cadet 2544 rider. If you killed the ignition at idle it would backfire so loudly it was painful, or it would diesel. If you killed the ignition per Cub's recommendation, which was throttled-up. No backfire, no dieseling. IMO, the condition results from the last bit of fuel working it's way through the engine after the ignition is killed. The hot engine or exhaust lights it off. They've all got fuel cut-off solenoids these days, but this only stops further fuel from entering the carburetor bowl. The bowl is still full at shut-down. If you're throttled up, the extra air leans out the mixture enough where it's not an issue (my opinion). Why it's more common on newer OHV engines I have no idea other than maybe they run hotter.

Long story short, shut the engine down per the recommendation in your Craftsman's owner's manual. I can almost guarantee your problem will stop if you kill the ignition at partial to full throttle.
 
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