Backfires When Starting...Engine Warm - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 24 Old 12-02-2007, 03:17 PM Thread Starter
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Backfires When Starting...Engine Warm

Hi All,

I've been using my tractor for leave sweeping and noticed that it backfires out the exhaust when I jump back on the and start it...Sounds like a shotgun. I adjusted the carb as per the manual and I thought I fixed the problem but it's back again.....I'm not sure but I think it only does it now if my throttle is low and I start it....

Tractor is a craftsman II 18 hp kohler..1993 model.

patch
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post #2 of 24 Old 12-02-2007, 04:11 PM
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Re: Backfires When Starting...Engine Warm

fuel entering the cylinder after shutdown (stuck needle? incorrect float level? I dunno)? If so, wont take too many more of those before something goes snap inside. If thats not it I am sure someone will be along with the exact fix for you shortly!
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post #3 of 24 Old 12-02-2007, 04:16 PM Thread Starter
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Re: Backfires When Starting...Engine Warm

Also, the only time it does this is when the engine is warm...When I start it cold it starts normal...

Could it be the way I start it? My throttle is low when I start it and the engine is warm...

patch
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post #4 of 24 Old 12-02-2007, 04:28 PM
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Re: Backfires When Starting...Engine Warm

Quote:
Originally Posted by patch View Post
Also, the only time it does this is when the engine is warm...When I start it cold it starts normal...

Could it be the way I start it? My throttle is low when I start it and the engine is warm...

patch
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I doubt the throttle set low has any effect since the butterfly valve (throttle plate) in the carb will be wide open at cranking speeds. If you are killing it at wide open throttle you might consider lowering the speed to low idle before the ignition is shut off. Maybar
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post #5 of 24 Old 12-02-2007, 04:50 PM Thread Starter
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Re: Backfires When Starting...Engine Warm

I always shut it off at low throttle....
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post #6 of 24 Old 12-02-2007, 08:05 PM
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Re: Backfires When Starting...Engine Warm

dont know if this applies to your year/model, but my 2003 kohler has an electric fuel shut off in the carb probably an air polution thing, has a visible wire coming out of the carb, might ck yours, dont know what year they started this, it must be shut down at 3/4 to full throttle for this to operate which doesnt sound correct, but it is, i know from experience and not completely reading my operators manual. if yours isnt equipped this way, i would go with a needle and seat sticking in the carb and letting fuel drip in after shutting off, but you would think the oil level would be over full after sitting for a week.
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post #7 of 24 Old 12-02-2007, 10:13 PM Thread Starter
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Re: Backfires When Starting...Engine Warm

I've been looking on the internet and found article about a john deere owner who had a similar problem and his turned out to be an ignition coil....Sounds to me like it's a timing issue..If it trys to start at the wrong time it will backfire....

Also, if fuel leaks into the cylinder wouldn't I have a hard time starting it such as engine flooding as opposed to a backfire?

Just trying to put 2 & 2 together..I could be wrong...

patch
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post #8 of 24 Old 12-02-2007, 11:32 PM
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Re: Backfires When Starting...Engine Warm

i guess you have looked and yours doesnt have a wire coming off the carb, just trying to start out with the simplest/most obvious before spending a bunch of money. if i remember correctly from reading posts, you purchased used in late spring? get an operators manual with it? have you tried your shut down and restarting proceedures yet? yours may be designed entirely different than mine. just trying to save a fellow member a buck. as far as a coil problem, it is either on or off momentarily, controlled by an electronic device or a set of points, usually if a problem occurs, you would have runnability problems. i wouldnt think timing problems should occur if it normally starts and runs correctly, unless something is triggering a coil at the wrong time, which is pretty unlikely. i dont know everything, but i would start with the simplest, due to my older age, been there, tried that, keep us posted, and try to keep the wife off your butt for purchasing something this old, [to me, not that old]. good luck.

Last edited by tjw in kans; 12-02-2007 at 11:44 PM.
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post #9 of 24 Old 12-02-2007, 11:51 PM Thread Starter
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Re: Backfires When Starting...Engine Warm

I just read posts about starting and stopping the engine as well as the manual. My manual says to start the engine (warm) put the throttle half way and turn the key. To shut down, move throttle to low, then turn key off. Read different posts, some throttle to low and wait a minute to shut down.

Since my issue is starting while warm I'll just shut it off when I'm done and not try to start it so many times...

And yes my wife did say not to buy an old tractor but I didn't have much money and I couldn't pass up the deal....she's not rubbing it in my face or anything since I bought an old tractor. Although I was expecting some kind of remark from her.

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post #10 of 24 Old 12-03-2007, 01:57 AM
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Re: Backfires When Starting...Engine Warm

Hello New here... reading your post. Hope you don't mind me sticking my nose in here ?
Throttle down and wait a minute is the right way for your tractor. That is so it don't build up gas in the manfold and back fire shutting down.
I would think repeated start up and shut down, in a short time could also cause this, even more so if your not shutting it down and/or starting the right way. Throttle down like you do but wait a 15 to 30 sec before turning the key off, and do the half throttle start up. Once your doing the way they want you to you might not have any problems.
You have a good cast iron kolher engine, the good old days......
Thanks for letting put in my 2 cents.
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post #11 of 24 Old 12-03-2007, 09:51 AM Thread Starter
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Re: Backfires When Starting...Engine Warm

Thanks for all your input...I'm going to take all your suggestions and see what happens...I'm hoping it's not the ignition coil. I'll need to take lots of parts off to replace that..

The other thing I was thinking about is that during the summer it never did this. This started with 1 backfire, then 1 here and there and now more often. It does this 1 out of 3 times.....

Also, this weekend while using it I was driving at 1/2 throttle which may or may not be causing this. I know the manual say to operate at full throttle but to me it's strong enough at a lower throttle....

I'll try my testing this weekend.

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post #12 of 24 Old 12-03-2007, 11:49 AM
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Re: Backfires When Starting...Engine Warm

A dirty air filter can cause a semi-choke rich fuel condition. Not that you don't have good maintenance practices but sometimes those things just sneeeeek up on us. Just a cheeeeeep thought. Maybar
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post #13 of 24 Old 12-03-2007, 11:55 AM
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Re: Backfires When Starting...Engine Warm

Quote:
Originally Posted by Small Fry
Hello New here... reading your post. Hope you don't mind me sticking my nose in here ?
No apologies needed Small Fry...That's what it's all about here....members helping one another out by brain storming a problem.

Welcome to the forum.

Randy G
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post #14 of 24 Old 12-03-2007, 07:32 PM
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Re: Backfires When Starting...Engine Warm

patch, it may have alot of carbon build up in the combustion chamber; cylinder head, piston, and valves. May have to decarbon with Sea Foam, or take the heads off and clean with a wire brush and install new head gaskets.
I say this because you say its fine starting cold... just a thought, Tony
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post #15 of 24 Old 12-03-2007, 07:39 PM
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Re: Backfires When Starting...Engine Warm

, Small Fry, on what Argee said! Enjoy the forum, Tony
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