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JD STX38 Oil/Fuel Leaking Problem

8 years ago

last modified: 8 years ago

Hi Tractor Experts - I recently inherited a John Deere STX38 blackdeck. All runs well except when I do a cold start some oil/fuel mixture shoots out of, what I believe is, the muffler. Does anyone have any recommendations on how to fix this problem? Would this be a broken gasket? It only seems to happen when the engine is cold. Common problem for this model? Any suggestions would be greatly appreciated. Thanks in advance!

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Comments (6)

rexlex
8 years ago
if your unit is set up with a gravity feed fuel tank, would suspect raw fuel getting thru the carb float valves and then leaking into your cylinder and/or crankcase. Simple way to chk is with engine cold, remove spark plug just before cranking to see if fuel spray is ejected... or pull oil dipstick and smell same for presence of gas in oil.
If so, change oil and filter right away to minimize engine damage; install an inline fuel manual shutoff valve until you can get carb repaired.
Another option is to get the Kohler engine numbers off the tag/decal on that engine and then check at kohler's website for appropriate service manuals that can help you troubleshoot other possible causes.
Good luck.
javert
8 years ago
This posting might show up twice, as I tried to post it a couple of
minutes ago, but the "new" Garden Web seems to have shipped it to outer
space.

Do what rexlex advised. Then, when you're ready to shut
your STX down for the day, leave the engine running, CLOSE THE SHUTOFF
VALVE, and let the engine die of fuel starvation. It will take the
engine a minute or two to shut down, but that's a good thing.
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Hey folks, so I'm posting this follow up in my original thread because I think I have a related problem. Last year, I replaced the PTO drive belt and the mower blade drive belts on my inherited JD STX 38 Yellow Deck. Today I took the mower out (NOT the first time this season) and had some serious issues. First of all, the grass is tall - 18-24 inches. I had the mower height set to the tallest height. The grass may have also been slightly damp - although not wet. I was able to cut basically one path, then I realized that although the PTO was engaged, the blades weren't cutting the grass. I was going at the slowest speed (first gear) and even tried cutting using only 1/2 of the mower deck width at a time - no help. I took the mower back to my driveway, cleared out lots of old clumped grass from the blades, and started the mower and the PTO. The blades were definitely turning. I turned off the mower again, and noticed that the PTO drive belt is looking terrible - it's all pitted and slack - it's not tight around the PTO shaft! So, my theory is this: the PTO drive belt is shot again (Although not broken yet) - so the blade spin when I'm not trying to cut anything, but when I come in contact with any sort of grass of substance, the slack belt is "slipping" and resulting in the blades not cutting? Does this make sense? Solution: replace the belt AGAIN???? A few more things to note: 1) I tried cutting shorter grass and drier grass and had very little luck. 2) why would my PTO drive belt, just replaced a year ago, be so shredded already? That's worrisome... any advice would be appreciated. thanks.
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so get this, folks - the same thing happened today with my "new" belt - the blades were unable to cut the grass and the grass is nowhere near as tall as it was last time. I tried to troubleshoot it, and was able to get the blades spinning again briefly, but the belt quickly failed again. When I turned the mower off, the belt was sizzling hot. Now, to be honest, I don't really have too much of an issue replacing this belt once (or even twice) a year - this is an old machine that I inherited, and I had no intention of putting any sort of money into it. Right now my solution has been to replace the $20 belt every time I have a problem - which I can live with. BUT: is there something else that could be causing my belts to fail so quickly? This time the belt is not pitted at all - it's just stretched, so that when the PTO engages, there isn't enough tension on the belt to turn the blades.. thanks for you help...
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mla2ofus
8 years ago
But be sure to turn the ign switch off after it dies.

Mike
BondBull
Original Author
8 years ago
This is great. Thanks everyone. I will look into adding a fuel shut off valve. I've been reading up on this issue and it seems this is a fairly common occurrence for my engine (13hp Kohler Command). When adding the shutoff valve should I place it between the fuel tank and fuel filter or between the fuel filter and carb? The first being my preferred method since it can be useful when swapping out an old fuel filter.

In regards to the carb itself what is typically required here? A good cleaning or is there a something in the carb that needs to be replaced (float needle, gaskets, etc.) I can't say I'm very familiar with carb rebuilds but a number of youtube videos walk through the process very simply. Any guidance here is greatly appreciated! THANK YOU AGAIN!
rexlex
8 years ago
shutoff valve between tank and filter is fine. And if engine quits acting up as described after you have this fix installed, then a good time to pull, clean and rebuild the carb st a convenient time using a fresh rebuild kit which includes the needles, gaskets, etc.
carb cleaning involves a complete teardown, overnite soaking in liquid carb cleaner, probing ALL passageways with a small dia stiff brass wire, then blowing out same with compressed air, then rebuilding carb assy using only fresh gaskets. clean is the name of the game here.
good luck
javert
8 years ago
My STX-38 has the shutoff valve between the fuel tank and the filter.

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