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White smoke, oil smells like gasoline

Posted by mustangm (My Page) on
Tue, Aug 3, 10 at 20:23

I have a Murray model 42544x8B with a Briggs engine model 28E707-0121-E1 code 9802112E. I have been having issues the past few starts where it is taking 15-20 seconds for the engine to start, and it starts with sputtering. Today, when it finally started the exhaust blew lots of white smoke. The engine stalled within a minute. I checked the oil level and it seemed abnormally high, so I emptied the engine oil. The oil was very runny/thin and smelled like it was mixed with gasoline. I really appreciate any advice you can offer. Thanks!!!


Follow-Up Postings:

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RE: White smoke, oil smells like gasoline

"Today, when it finally started the exhaust blew lots of white smoke. The engine stalled within a minute. I checked the oil level and it seemed abnormally high,"

You mean you don't check the oil level each time before starting the engine?

The carb float needle has obviously leaked allowing the oil to become contaminated with gasoline and will ruin the engine if run that way. Oil should be drained and refilled with good SAE 30 oil.

Then an in line gas shut off valve should be added to the gas line and used whenever the engine is not running. Replacing the carb float needle MAY help but shut off valve is still best insurance anyway.

IF there is smoke after doing this then it is likely the head gasket has blown, check for oil in air filter box.

Walt Conner


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RE: White smoke, oil smells like gasoline

Yep another "Future Small Engine Mechanic" Well for what its worth you just learned Rule #1...Check Your Fluids prior to Starting "OIL 1st" !!


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RE: White smoke, oil smells like gasoline

  • Posted by baymee LehighValleyPA (My Page) on
    Wed, Aug 4, 10 at 5:53

Just yesterday I worked on an MTD tractor with a Briggs 14HP OHV engine. The guy "crashed into a fence". There was oil all over the frame, on the ground, and dripping from the muffler. The air cleaner box was full of oil and white smoke was pouring out of the muffler. The oil was about a quart low.

I looked for any engine damage and found none. I started the engine and the white smoke poured out for about 5 minutes and then stopped. Added a quart to the engine and ran for another 20 minutes...no problem at all. Moved to a shed and not a drop of oil anywhere.

What could have happened to cause all these symptoms and now, nothing?


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RE: White smoke, oil smells like gasoline

Was the engine stored on it's side?


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RE: White smoke, oil smells like gasoline

Either what Roadbike said is true or during the incident the tractor high-sided (turned over) for an extended period of time . No other way to have Sump Oil enter the Intake Combustion Chamber or Exhaust Systems ?


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RE: White smoke, oil smells like gasoline

  • Posted by baymee LehighValleyPA (My Page) on
    Wed, Aug 4, 10 at 16:59

If Dad's mower was turned on it's side, the young lad isn't saying.


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RE: White smoke, oil smells like gasoline

Well my grass was getting too high so I finally got around to addressing this issue. I drained the oil, pulled the spark plug and cranked the engine to remove any excess oil/fuel. I pulled the carb, blew air through all holes and replaced the float needle (I have never seen a float needle with a rubber tip before). I also installed a new fuel line, filter and an inline fuel shutoff. I added a good SAE 30 oil, replaced the plug and the engine started right up. For a few minutes there was white smoke coming from the exhaust. Everything was working pretty well until I got into the high grass. The engine struggled several times to the point that it was going to stall. After making several passes at the high grass the job was done.

Out of curiousity I went and bought a compression testing guage. I followed the instructions and the results were consistantly between 50-60 psi each time. I thought maybe I did not have the tool tight enough in the spark plug hole, so I reinstalled it several times with the same results.

Could this be the result of running the engine with oil/fuel mixed? How do I identify the source of the compression loss? I am thinking this could be a winter project.

Thanks for any advice.


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RE: White smoke, oil smells like gasoline

Well if all testing was done correctly either you have a valve hanging , head gasket leakage or the rings have been burn out of it . That is very low compression . Ensure that you are getting a good seal on the compression tester .


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RE: White smoke, oil smells like gasoline

"Everything was working pretty well until I got into the high grass. The engine struggled several times to the point that it was going to stall. After making several passes at the high grass the job was done."

The only problem I see is you need to mow more frequently.


"Out of curiousity I went and bought a compression testing guage. I followed the instructions and the results were consistantly between 50-60 psi each time. I thought maybe I did not have the tool tight enough in the spark plug hole, so I reinstalled it several times with the same results. Could this be the result of running the engine with oil/fuel mixed? How do I identify the source of the compression loss? I am thinking this could be a winter project."

It's a winter project only if you want to run the real chance of ending up with a non-functioning mower. The machine likely has some compression loss and I suspect it is not being measured correctly.

You do not have a compression problem worth worrying about if you can start the mower and mow weekly. Get back to cutting grass already!


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RE: White smoke, oil smells like gasoline

Mus: How tall is "Getting too High" 3-4 " should not pose a problem for a 14 HP tractor with usable Compression . How is the Oil consumption ? Any noticeable exhaust smoke during your cutting especially when you encountered the taller sections of grass ?


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RE: White smoke, oil smells like gasoline

I am thinking head gasket.

Walt Conner


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RE: White smoke, oil smells like gasoline

"The only problem I see is you need to mow more frequently"

Yep, I agree. I had let the grass grow for over three weeks until I had the chance to address the mower issue. A section in the backyard had grown to about 10 inches high. I probably missed mowing this the last time out.

"How is the Oil consumption ? Any noticeable exhaust smoke during your cutting especially when you encountered the taller sections of grass ?"

First restart after adding new oil the exhaust blew white smoke for about 2 minutes. I cut grass for over an hour and did not notice anymore smoke even after a few more restarts. After coool down I checked oil level and it was down from "full" to "add oil". I added a few more ounces to bring level to full. I am curious to see if this will happen again next week.

As far as testing compression, I will try again next week. Is it absolutely necessary to test compression when engine is at normal operating temperature? The last test I did I cranked the engine for about 5 seconds, the guage read 60 psi. I left the guage on for 5 minutes to see if the psi would drop, but it held consistant. I was thinking that if I did not have the tool connected securely, that the psi would have dropped over the 5 minute span.

Thanks for the help!!!


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RE: White smoke, oil smells like gasoline

Walt : I'am with you on the Head Gasket for Low Compression . But Heck should be a lot of Smoke with the Oil Consumption he is indicating ? Unless there is a puddle on the ground lol ?

Mas: Yes When engine is Hot Sealability is at it's best Rings and Oil both expanded and up to temp . I think you Gauge may be suspect . 10" of Grass hopefully not Wet ? I don't know something does not add up . Keep Cutting let us know further , and keep an Eye on the Oil Level I hr and level from full to add not good !


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RE: White smoke, oil smells like gasoline

I have just joined this forum tonight because my wife, who is 600 miles away, is having an issue with her garden tractor. It sounds as though there are some educated mechanics following this forum and I could use a little help. She is outside as I type trying to start the tractor so I would appreciate any quick help I can get. I don't know the name of the manufacturer but it is the run of the mill type you'd find at Home Depot or Lowe's, about a 15 year old. When the mower quit running last week, she drained the fuel tank, replaced the fuel and air filters, and checked all other components for damage. When she cranked it up, it ran great until tonight. She got it hung up on higher grass and killed the mower and cannot get it restarted. It will crank and backfire. It backfires constantly as she cranks but refuses to start. My brother says it sounds like the timing is off but neither of us is aware of any timing adjustment on a mower engine. Any ideas?


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RE: White smoke, oil smells like gasoline

peach: Off the cuff sounds like the timing is off . Since see was cutting tall perhaps wet grass and the mower stalled . Its quite often like striking a object and the flywheel sheer pin will shift (bend) although not completely shear . Just enough to prevent starting and causing the back fire situation . A blownhead gasket from lugging shall normally permit starting but will smoke and backfire as you have indicated . Don,t have anything further I can add perhaps when you get further info you can post it for the other forum experts Eg: Model and serial numbers would help .


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RE: White smoke, oil smells like gasoline

I've read these post and some are helpful, some are not. With my tractor, I started it, it ran a couple minutes while sitting then I heard a "pop" sound and white smoke poured out of the exhaust. It then quit running within a few seconds. The oil is full of gas and there is oil on my air filter. The air filter was replaced the day before... this was the first time the engine was run with the new filter. I can see gas laying in the carburetor. I will drain the oil and replace along with the oil filter. I will also replace the gas filter and will put in an inline shut off. Essentially do what was suggested above.

My question is, after doing all this, I will I know if there is a problem beyond that? I'm not a small engine guy. I don't want to totally destroy this engine if it's repairable.


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RE: White smoke, oil smells like gasoline

KayDan-
Is your engine a flathead as in the OP's or an OHV engine.

Model#'s help identify WHICH engine.
IF OHV, your symptom MIGHT be a blown head gasket. IF NOT, likely something broke.
Does the engine still rotate?


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RE: White smoke, oil smells like gasoline

Bill, sorry about that. I had the info but forgot to post it. It's an OHV, 16.5 HP. I have the model# , etc. but not with me. If it's the gasket, is there a simple way to test to determine this?


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RE: White smoke, oil smells like gasoline

Usually, if you remove the valve cover (have a rag handy) and start the engine, you'll see a "mist" blowing out on every power stroke. It's MOST often on the push rod side of the cylinder.


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