The old gas in the oil trick again

cmrussoNovember 4, 2013

Hi All,

Brand new to posting in this forum but I've read and learned a lot from all the great info here. But I've got a question puzzling me.

Recently, I purchased a walk behind mower with a 13hp Briggs Intek engine (21a907-0153-e1) for home use. Got a good deal since it wasn't running at the time and the owner wanted it gone. Got it home and ran through it and found no surprise a crankcase full of oil mixed with gas obviously from a sunk float or bad needle seat. I proceeded to remove and clean the carb. Drained the contaminated oil. Put her all back together and it fired up just fine. Cut the lawn and put it back in the shed. About a week later it had a crankcase full of gas oil again. So I thought to be sure of this I left the intake from the carb to the head disconnected overnight to see if the fuel still overflows from there. Not a drop came out?

Could this overflow happen when its running? The motor also has a vacuum fuel pump, could the fuel enter the crankcase from there if an internal diaphragm was bad? Kinda stumped...Anyone have any ideas

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gator_rider2(z8 Ga.)

Float adjustment when removed intake carb at same level and float cut gas off scale build up on float and sink just enough to let gas over fill bowl..

    Bookmark   November 4, 2013 at 4:52PM
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Did you flush the fuel line before reinstalling the needle.
Often there can be crud in the fuel line that get's broken loose when removing the line.

Chances are, when you disconnected the intake, the float may have gotten "jiggled" just right to seat the needle properly.

IF it was only leaking when running, it would just run rich, and possibly flood out if it was leaking severely.

When the oil ends up in the crank case, it's ran into the cylinder and then past the rings.

    Bookmark   November 4, 2013 at 7:20PM
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Yeah that's probably what happened. I did clean the lines and the tank pretty well but you never know. I think I'll get a new float and needle and try that. Gator mentioned that just a small amount of scale buildup on the float could sink it just enough to drop the needle. Hmmm.

    Bookmark   November 4, 2013 at 8:15PM
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cmrusso - Bill and Gator are most likely right on suspecting the carb needle/float. But if that doesn't fix the issue, go back and take a hard close look at the diaphragms in that fuel pump for cracks that might be letting raw fuel pass thru into crankcase while working...

    Bookmark   November 5, 2013 at 10:01AM
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