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MTD mower starts but then pushes fuel/oil out air intake on carby

Posted by rangerdave Australia (My Page) on
Sun, May 17, 09 at 4:25

Got mower for free and had a go fixin, had been sittin ~ 2 yrs, sump full of fuel when I got it so I assumed needle/seat fouled and cleaned a little, drained sump, then tested operation by pushing float up with fuel in it. Sure enough fuel stopped and started with adjusting float level, so put it back together, fired it up and away she went!

It was very smoky but thought that was from sittin so long and let it run bout 20s, then, started to die down and all of a sudden oil and fuel starts sputtering out air filter intake and all over engine(had filter off to view inside for fuel leakage). So I'm a bit confused but came to conclusion musn't have gotten all fuel out of sump and it ignited from below and somehow pushed itself backwards??? So, oils down now and I top up oil, fire it up again - same S***!

BTW, what's the little switch for below the carby reservoir housing the float?

Extra info: MTD 155 1/C, 18 HP "Black Beauty" from Bunnings, 42" cut, Briggs eng 28q777, type 0624-01, code 960628zd, float had no holes, did valve clearances, new sparkplug, new oil (but when it pissed out new oil, I topped it up with 20W-40 car oil thinkin I would just get it running then drain it out later and put the SAE 30 in)

I'm no mechanic and would appreciate any and all help - thanks!

Anyone got a repair manual for one of these?


Follow-Up Postings:

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RE: MTD mower starts but then pushes fuel/oil out air intake on c

"what's the little switch for below the carby reservoir housing the float?"

That is an electric solenoid valve that shuts off the flow of fuel thru the main metering jet to prevent "after fire" when shutting engine down hot.

"1/C, 18 HP "Black Beauty" from Bunnings, 42" cut, Briggs eng 28q777, type 0624-01, code 960628zd,"

Someone has been having fun. A Model 28p777 B&S Engine would not be 18 hp. but that is not your problem. IF it has a fuel pump, it may be bad causing gasoline to leak into crankcase.

Walt Conner


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RE: MTD mower starts but then pushes fuel/oil out air intake on c

Thanks Walt - appreciate your input - Was under the impression it didn't have a fuel pump as I figured it would be between tank and carby and I can trace line through to there without seeing any pump. Further, the tank is positioned above the carby so would think it wouldn't need one - Am I right? I'll check that 18 HP too...


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RE: MTD mower starts but then pushes fuel/oil out air intake on c

If it is pushing oil out through the filter, You have a pressure buildup in the crankcase. Could be as simple as overfilling or as complicated as worn rings causing excessive blowby.


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RE: MTD mower starts but then pushes fuel/oil out air intake on c

Check the float, to see if it floats. Sounds like that may be your problem. I remove the float and float it in some gasoline, for an hour or more. A teeny pin hole will cause a no-float position. Like the bottom of the bowl? Yep! And that will give you a lot of trouble.


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