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



## Davo (May 17, 2009)

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) Quickly shut it off! So I'm a bit confused but came to conclusion musn't have gotten all fuel out of sump and it ignited and somehow pushed itself backwards??? So, oils down now and I top up oil, fire it up again - same S***! 

So then I take out spark plug, drain sump, from little plug below oil filler/dipstick tube, and crank over engine thinking this should flush out any fuel in there. Even though I didn't have spark plug in lead, the fuel that's bein kicked out spark plug whole lights up and all the bit that was all over mower lights up and suddenly my mower is a ball of fire!!! While I'm scramblin for a blanket or something to put it out, my kid comes running over and turns the garden hose on it and me! So, lesson learned, I clean the whole thing out, remove the wiring for the lights that is now melted together, crank the engine (with the lead covered up with a rag and out of the way) to confirm there's no fuel still in the cylinder, fill it halfway full of oil, and start it up - Same s***! 

So now I test the float switch again, seems to be working, install a fuel line switch, which I keep in closed position, and try it again - Still oil/fuel bubbling up through carby! What the f***? This time, I let it run a little longer and smoke keeps pushin through exhaust, bubbling stops, but now I figure I'm probably running it without oil, get scared and shut it off cuz I don't want to totally mess up the engine. 

Please HELP! What's wrong and how do I fix it? 

BTW, what's the little switch or sensor for below the carby reservoir housing the float – Fuel light? (actually clamps reservoir over float and has an extendable pin that pushes up under float – 2 wires go under engine and 1 traces to main cables)?

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?


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## Live Oak (Dec 22, 2003)

Welcome to Tractor Forum Davo! Sorry to hear about the tough time this mower is giving you, especially the fire. I am just taking a SWAG here but have you checked for a blown head gasket? Another outside possibility may be the piston rings are shot to the point of allowing large amounts of combustion gas to blow by and pressurize the crankcase. This could be causing the oil and gas to blow back up through the carb. 

A bent or leaking intake valve would allow combustion blow back through the carb but I would think NOT the oil.


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## Davo (May 17, 2009)

*Thanks bud!*

Appreciate that - thanks, I haven't checked for those things - primarily as I don't know how. But WTF, nothing ventured nothing gained right? Do you know how to get that flywheel off perchance? Require some special tool?


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## SHARTEL (Feb 11, 2009)

I agree with TF Admin!

Blow back from a source of positive crank case pressure could be from stuck valve, back head gasket or cam shaft lobe wiped away. 

A compression test would be my first course of action.

The flywheel needs a rather large 3 finger puller.

Good luck and keep us informed will ya' ??

SHARTEL


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