I recently purchased a freshly serviced used John Deere LT150 and mowed the lawn for the first time today cutting roughly 1/2 acre. It starts beautiful and runs smooth, my question is that during the process I turned off the engine a few times and each time the engine (15hp kohler) had a single loud knock and some afterrun or backfire. It would start right back up when I was ready to go again but I'm concerned this is not normal...what should I be looking for?
HELP! JD LT150 w/knock when turned off?
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aczlan
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Did you idle down before shutting the engine off?
In my experience, shutting off from more than an idle will cause a backfire.
Aaron Z
In my experience, shutting off from more than an idle will cause a backfire.
Aaron Z
aczlan
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Give it 15-20 seconds at idle before shutting it off. That will also allow the engine to even temperatures out a little before you shut it down.
Always makes me cringe to see someone shut a machine off from full throttle...
Aaron Z
igpoobah
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I have an LT 150 and you have to let it hit idle before killing it or it will knock and sound like crap as it shuts off. Normal.
I know it is not what we were taught from the day we started using gasoline powered equipment, but instead of idling down and then turning the engine off, leave at about three quarters throttle and turn off.
The new engines seems to want to backfire and make strange noises when shut down at idle. The backfire can be so severe as to cause damage to the exhaust system.
The new engines seems to want to backfire and make strange noises when shut down at idle. The backfire can be so severe as to cause damage to the exhaust system.
jinman
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Have you tried premium fuel? It sounds like the engine may be dieseling a bit when you shut it down. Super premium fuel has higher octane and should stop the issue, especially if you let the engine idle down and cool off a few moments before shutting off the engine. The newer engines with fuel cutoff solenoids will instantly shut off fuel and cause a lean mixture that may cause backfiring. Autos have used an anti-backfire valve to dump loads of fresh air into the exhaust when decelerating or shutting down so that the fuel will not ignite.
UPDATE on LT150 Knocking...
Thanks again for posting suggestions...the answer was as several of you thought...it needs a good 20 seconds to run at minimum idle before turning off. Todays experience was smooth & quiet, and it was a joy mowing the lawn.
Thanks again for posting suggestions...the answer was as several of you thought...it needs a good 20 seconds to run at minimum idle before turning off. Todays experience was smooth & quiet, and it was a joy mowing the lawn.
