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So I have a Craftsman riding lawnmower with a 16 HP B&S single cylinder OHV engine. It was given to me by a neighbor last year. It had stopped working and he had purchased a new John Deere, and just wanted it gone, so he was happy I took it. So it sat in my garage for this year collecting dust while I worked other things, but was finally able to find time for it a couple months ago.

So the battery was dead of course, I charge it up and give it a spin. Now keep in mind, I never got any information from the previous owner as to why "it wasn't working". So I turn the key and see that the starter is laboring to spin the engine. With a little bit of help from me she's able to kick off and cough to life, albeit a smokey and stuttering life. So after a few minutes the smoke cleared and everything seemed pretty good.

Fast forward a few months, I've given the lawnmower to a buddy of mine who needed one who has used it a dozen times over the summer. I had been meaning to get over to his house to address the starter laboring issue for some time and finally made it over today.

So I started with the valve lash adjustment to see if that could be causing what appeared to be an over compression issue. When I popped the valve cover my first comment was "wow, that's really thin oil!". Well, it wasn't oil, it was gas. Having never seen that before, I cleaned it up and completed the valve adjustments. When I was done and everything was all sealed up, I was interested to see if this would solve the problem. So I turned the key and while still slightly labored, the starter was able to turn the engine over without assistance. So after letting the engine run for a few minutes I shut it down.

It was at this point that I started thinking about that fuel in the valve cover. I checked the oil on the dipstick just to see what it looked like and could definitely smell fuel. So at that point I decided to drain the oil out of the crankcase to see what it looked like.

Well, I wouldn't have believed it had I not seen it. When I took the oil drain plug out, black tinted gasoline came pouring out filling up two 2 liter Coke bottles! This stuff had absolutely no oil-like viscosity or properties at all. So for the last 2-3 months my buddy was running this thing with raw liquid gasoline in the crankcase, and it didn't seize...or explode!!??

So no, neither of us poured gasoline in the wrong hole, but I cannot rule that out for the previous owner.

My question is, does anyone know of a maintenance issue that would cause raw fuel to be dumped into the crankcase at that volume (3-4 liters)?

We put oil into it and are going to keep an eye on it for the rest of the season. This winter I'm going to tear into it to see if any internal damage was done.

Any comments are much appreciated.

BN
 

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Well the carb fuel inlet is leaking allowing fuel into engine and diluting oil. A common issue with Briggs single Intek engines. A carb rebuild will solve this. Did you ever check the oil since you got it? The level should have been too high with gas in it. By using it, the internal bearings and cylinder bore are most likely worn out.
 

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Discussion Starter · #3 ·
Ok, good to know. I'll tell my buddy not to use it until we rebuild the carb, easy peasy. I'm thinking that the fluid in the crankcase, valve guides, and cylinder could have caused the high compression, does that sound right?

As far as checking the oil, yeah I did. Not sure about him, but if something seemed out of sorts, I would not have run it. When I tear into it this winter I'll update this thread with the damage I find. Thanks for the reply!
 

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Had the same thing on my Briggs 15.5 OHV. Gas tank higher than carb. The older mowers had a shutoff valve on the fuel line. Carb rebuild is good idea.
 

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:ditto: To prevent future problems, I'd add a generic shut off into the line after you redo the carb.
Absolutely do this! I buy those shutoff valves by the dozen on Amazon now, and install one on every mower (even walk-behinds) that has the fuel tank higher than the carburetor.

The exact same thing has happened, multiple times, to my neighbors' riding mowers. I have installed shutoff valves on all of them. If you don't get enough of the gas out of the crankcase, it will ruin the rod bearing in just a few minutes (happened to two of my neighbor's mowers, even though they did change the oil after this happened). So I'd do at least two oil changes, with the second oil change after running the mower for a minute or two under no load.
 

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The OP's question and the scenario he details above reminds me of something that happened to me just recently that still puzzles me, and I'm curious as to whether or not any of you might have any insight on this one:
I reworked a walk-behind (not a rider) with a little Tecumseh TVS90 - cleaned it all up, carb overhaul, plug, oil, air filter, blah blah blah....
The thing sat in the garage for 5 weeks before somebody finally called on it.
During that 5 weeks, I went out there every few days and rolled it out onto the driveway and pulled the rope and let it run for a minute or two. Started right up every time. Ran perfect.
So the guy comes over to buy it, takes it home, brings it back the next day saying "no power!"
Thing runs perfect. I forgot to show him it had a manual throttle control, and he must have bumped the throttle control lever and had it idling way down without realizing it. (i.e., "no power!")
So just to make sure I haven't missed something, I pull the plug - it looks fine. I pull the oil fill plug - full up and then some - so I stick my finger in there and take a whiff - and smell gasoline. WTH?
So I tell him "Leave it here overnight, I want to change the oil."
I am baffled at this point. Thing ran perfect. No leaks, drips, or smoke.
So I drain the oil - let it drip all night. Refill the crankcase, pour some gas into the tank, and yank the rope. Gas spits out of the muffler all over the deck. WTH?
So I rip it all apart - pull the carb - pull the bowl off and shake the float - splishy-splashy - I got a float full of gas.
Dig around in the garage for a new float, put everything back together, and all's good.
Call the guy and say "Come and get it."

Is it possible that thing was seeping fuel down the intake pipe the whole time (for five weeks) and (if the intake valve were open) allowed fuel to enter the combustion chamber and gas leaked into the sump past the rings?
I know, I know: anything's possible inside a gasoline-powered internal combustion engine - (I should know - I spent seven years selling them for a production automotive engine remanufacturer) - but this one was just whacky.

Let me add here: When I'm done with these things, I run them for at least a couple hours to make sure everything's A-OK. Ran two tanks of fuel through this one. And then (again) went out every few days and ran it for a couple minutes. No problems.
The customer said he "only mowed two passes and then it just lost power!" (Again, he wasn't aware it had a manual throttle control - my fault for not showing him assuming he would know that.)
In all that time there was no fuel leaking from the bowl, and certainly not gas puking out the muffler.
I am still baffled by that one. The guy's had it back now at least a week, so I'm assuming everything's okay now.

Any thoughts?
 

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I suppose it is possible that the float was slowly filling itself up during that time, and finally reached the point that it was no longer able to do what it was supposed to do by the time it passed into the hands of the new owner.

All of this brings up another point too. It is important to go over the features of anything sold to another person. When I was flipping mowers, I'd spend a few minutes telling the person buying the mower what I had done to it, how everything operated, and I'd either give them a printed copy of the owner's manual that I had gotten off of the internet, or at the very least, told them where and how they could obtain one.
 

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Agree with what Bruce concluded...As for muffler spewing gas...Maybe owner tilted it up on side, wrong side up...filled the intake and combustion chamber, [many owners do NOT know what side up when tilting]---saturated plug won't fire...then his cranking or pull starting forced the gas into muffler...Heck,,,All's well that ends well..!
 

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As the owner, operator, and head mechanic of a vintage motorcycle that has a gravity feed fuel system and four carburetors (one per cylinder), I've had to contend with a lot of "fuel in the crankcase" issues over the past 30+ years. I finally replaced the automatic petcock with a manual version and eliminated that problem with my motorcycle.

So naturally when my mower showed signs of gas in the oil, the first thing I did was to install a new float and needle. Once I had changed the oil and filter I was off to mowing again. Well a few days pass and I have gas in my oil again. I remove the carb and inspect it to insure there's no problem with the function of the float and needle valve. Everything is fine so I reassemble and change the oil and filter again. I come to the conclusion that it must have been a hanging/stuck float as the mowing season ends. The next spring I mow the yard a couple of times and discover gas in my oil yet again. At this point I'm frustrated with the whole mess and decide to install a shutoff valve in the fuel line. I continued to get gas in the oil after installing the shutoff valve and continued to change oil and filter a few more times (I needed to mow and this mower was only 2 years old when this started so I wasn't ready to replace a mower that I had just paid $2400 for 2 years earlier). So one day as I prepared to mow, I checked the oil and everything was good to go. I started mowing the yard but before I could finish, the mower started blowing white smoke and died. It only took a quick look to verify that it had gas in the oil again. At this point I concluded that the gas was entering the crankcase while the motor was running. Logic dictated that this couldn't happen via the carb or the engine would have been too flooded to even run, much less mow during the process. Then it hit me, the fuel pump is vacuum driven and another possible point for fuel to enter the crankcase. I pulled the pump off and opened it up. Sure enough, there are 2 small holes in the diaphragm. So lesson learned, there is another possible source of fuel if your mower has a vacuum driven fuel pump.

BTW my "3 year Toro warranty" doesn't cover the fuel system. Check the fine print when you buy a mower these days.
 

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Hey, Newbie here. While this thread is sold, it's right in line with a problem I'm having with a 15 year old Briggs on a Snapper 33" RER.

Original problem was that I can't turn over the engine when starting due to too-high compression. Electric or Manual turns. Ran machine for 15 years now, and problem only manifest itself when I went to start it for the weekly mowing.

Now I know there is a a small lever on the camshaft, with a spring which reduces the compression for startup purposes.

I'm not in a position, either by training or tools or money to have this serviced. First advice was to adjust the intake and outake valve gaps. When I pulled the valve cover off, it was full of gas. Not knowing any better, I set the valves to their proper gap, drained and replaced the oil. Still has high compression, can't start. Had to get another mower at that point, but would like to repair this one myself.

I know you guys are talking about a carb rebuild, which I had done professionally a year ago. Understand that the bowl, pin or solenoid it still could have failed.

So I might have two problems here, correct? 1) Gas in Oil and 2) high pressure at start. I'm disinclined to pull everything apart and replace this low-compression lever, which presumably means replacing the whole cam. Do I have this right?

BTW, I put a fuel shutoff valve on the engine years ago.

Thank you!
 

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I have a small fleet of carbureted machines (well over 20), and over the years I have learned to always cut off the fuel anytime the engine's not running. For this to work, a fuel shut-off valve needs to be present.

Generally speaking this problem is due to the carburetor's float bowl mechanism failing to shut off the fuel supply, unfortunately it is not only a common problem but it also tends to occur with little warning. Also unfortunate is the fact that over time this issue can definitely wreak havoc on an engine.

Last but not least, anytime fuel has gotten into the oil an immediate oil and filter change is required if you wish to prolong the life of the engine, however one should not assume this to be the end of the repairs... I would advise to address the leak and change the oil and filter, all before the machine is ran again.

This issue happens most often after the mower has sat for some time, usually at least overnight. If the issue happens after it's only sat for a few hours then the problem is more severe and should be dealt with immediately. The seepage need not be tremendous, one may not notice any gasoline missing out of the fuel tank, it may not cause flooding while it runs either, even a pint of fuel leaking down over three days time can cause quite the issue. First off checking the oil regular is always helpful, while so doing one might take a whiff of the oil. If fuel is present its odor is rather distinct and leaves little to guessing, either it's there or it isn't.

A definite sign of fuel leaking into the oil is hydrolock, most noticeable by two things:
1. The engine is hard to turn over, it may even appear seized up.
> If this is the case, removing one (or both on V's) spark plugs and turning it over with the spark plugs out should help empty the chamber(s). It may take some time to dry it out good so that it starts without flooding.
2. Fuel comes spitting out of the exhaust (may look like any other liquid such as condensation, but if it sprays out it's almost always fuel).
This is because one or both cylinders have gotten flooded, basically the carburetor has failed to shut down the flow of fuel, allowing it to get into the engine which is also how the fuel gets in the oil.

So...
One solution is to drop the fuel bowl carefully (parts may come falling out), and with one hand cupped over the mechanisms to keep parts from flying spray some carburetor cleaner up in there, hopefully that loosens things up... Or just replace the carburetor.

Unless it has one, install a fuel shut-off between the carburetor and the fuel tank.

And...
Anytime the engine is shut off, learn to cut off that fuel shut-off valve.
That helps prevent a ton of this occurrence, it's really helpful in keeping down the cost of unscheduled oil changes.
 
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