B&S 16.5 OHV Stalling

helpinganeighborAugust 21, 2010

Hello, My neighbor has a Murry lawn tractor with a Briggs & Stratton 16.5 OHV 313777 - 0112- E1 engine. It starts fine when cold, and runs well until it warms up. Then the governor starts surging back and forth and the engine stalls. It will restart but won't keep running. If you put the choke on when it's surging, it will keep running. When I looked at it for her, I noticed that someone had put what looked like twice the oil need in the motor, all the way up the stick covering the DO NOT OVER FILL warning! So I drained and filled to the proper level hoping that would fix it, but it did not. I cracked the gas tank cap to make sure it was venting properly, but no different. Does anyone have any ideas as to what could be wrong? Could the bleeder be clogged? Or could the engine be seriously damaged from the overfill? Thanks, Tom

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"I noticed that someone had put what looked like twice the oil need in the motor,"

Most likely this is the result of the carb float needle not seating and flooding the engine with gasoline which then leaked on down into the crankcase oil. Very common and will ruin the engine if run this way for any period of time. It needs an inline gas shut off valve installed and used when the engine is not running.

Now as for the stalling, sounds like it is running lean. You need to check some things. Does it have spark when it dies? Is it getting gas? Does it have compression? Did you remove and drain the carb float bowl, may have water, crude in it.

Walt Conner

    Bookmark   August 21, 2010 at 12:03PM
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***" I noticed that someone had put what looked like twice the oil needed"***

Did you smell of the oil for the presence of gasoline?
Did you simply "pull the dip stick and read it" or did you "pull the dipstick, wipe it off, and reinsert it, pull it again and read the second pull"?
If you simply "pull and read" the oil level on a cold engine, the oil trace on the stick can sometimes be at a higher level due to thermal vacuum after the engine cooled following the last running.
Does this tractor have a fuel pump? or is the gas tank higher than the carb?

Do you know if this "condition" has been coming on for a while and has just now reached this level, or if this happened suddenly with no prior problems?

Engines that peter out like this when they warm up can be suffering from the cooling air flow across the cylinder being blocked by mice activity, they like to get under the sheet metal shroud and build nests or sometimes cache food stuffs in there. Would not hurt to rule that out as a cause. Pull the shrouds and inspect under there.

    Bookmark   August 21, 2010 at 12:10PM
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Thanks guys. Here's a few more details. I triple checked the dip stick, wiped clean every time, the oil level was extremely high. I filled a 64oz bottle emptying it. I believe the capacity is around 40 to 48oz?. I didn't notice the smell of gasoline and the oil didn't seem too thin, but I wasn't really checking for gas. Hard to tell now, it's in an old milk jug and I don't know what I'm smelling. I will say the oil level has remained at the proper level I filled it to and has not risen in the time I've been running it trying to fix it.

I am able to keep the motor running when it begins to stall by engaging the choke. That leads me to believe there is still a spark, compression and a fuel supply.

The gas tank is higher than the carb, but the carb has a fuel solenoid on the bottom of the bowl. I believe it is a fuel shut off valve? Replaced for $37.50, no help. Though it might be failing when it heated up.

I have not check for the rodent factor yet, but will see if we have anybody nesting in there. Or that may have been in the winter.

Could there be something sending a bad signal to the fuel solenoid? And could turing the choke on change it?

They say DO NOT OVER FILL, what happens when you do? Could the engine have been damaged?

Is there some type of bleeder valve like I remember on the old motors? And could it be clogged from the oil being over filled and causing the problem ?

Thanks again.

    Bookmark   August 21, 2010 at 5:12PM
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I'll try to clear away doubts and misconceptions.
There is no signal to the fuel solenoid except for the 12 volt current when the key switch is turned on. If the fuel solenoid were bad, or losing current, you would not be able to coax the engine into running at all.
There is not any kind of "bleeder", but there is a crankcase breather, if that is what you refer to.
It is unlikely that over filling the crankcase with oil has damaged any of the "hard parts" of the engine, though it might have contributed to a head gasket failure. But head gasket failure typically causes the engine to smoke like a chimney out the exhaust as the chief complaint. Are you seeing copious amounts of white smoke that you didn't mention?
You say the condition comes on when the engine warms up. About how much elapsed time are we talking about from cold start to surging and stalling? Give the time in United States minutes. :^)

    Bookmark   August 21, 2010 at 6:28PM
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Thanks mownie. Didn't know if there was any connection between any of the safety switches and the fuel shut off, but as I said, it's my neighbors rig and I haven't dug too deep just yet.

And I meant breather, Doh! Could it be clogged and causing the problem?

Haven't noticed large amounts of white smoke. But haven't looked too closely. Could a blown head gasket cause the problem?

From a cold start, I'd say it takes 3 - 5 minutes, Eastern Standard time. Maybe less if I drive it around, even quicker with the blades engaged. It was long enough for the components like the fuel solenoid to get hot. I'd heard that when they start to go, they start failing when they heat up initially. That's why I went after it, sounded like the perfect suspect. But what do i know, obviously!

    Bookmark   August 22, 2010 at 9:42AM
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Well this has all been very interesting and taken up a lot of space but I don't see any answer to the 2 - 3 simple tests I ask about.

Walt Conner

    Bookmark   August 22, 2010 at 1:09PM
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Before we start guessing, you need to do the tests suggested by Walt.

It is not unheard of for a magneto (coil) to become weak and not be able to fire off a spark when conditions inside the cylinder change. So, a check for presence of spark should be done when the engine dies. This kind of test is more meaningful if the genuine Briggs spark tester is used because that tool allows the spark plug to remain in the head and thus the effects of Combustion pressure and cylinder temperature can still influence the "sparkability" of the coil. Simply checking for spark by laying a plug out on the engine does not allow for those influences. But you still need to check for spark any way you can when it dies.
Temperature changes and the effect of increased compression pressures can literally suppress a spark from ocurring in a warm engine.
Applying some choke will have a direct effect on the compression pressures in an engine (make them lower) and that could be why the engine is "smothering down".

Another thing that could cause the engine to die out is starving for fuel. If it is dying due to lack of fuel, you can determine that by spraying a short burst of spray carb cleaner into the carburetor throat as soon as the engine dies. If the engine tries to run strong for a second or 2 and dies again, there is a fuel delivery problem. If it is from too little fuel, pulling the choke will keep it running because the choke is reducing the volume of air that can mix with the insufficient fuel volume. The engine might not die with the choke pulled, but it will not make much power either.

Another thing that could be killing this engine is an exhaust valve that is too tight (too little clearance). if this were the case, when the valve heated up, it would not seat completely and compression would be lost out the exhaust, resulting in the engine losing RPM and power. This is why you need to check compression when it dies.

    Bookmark   August 22, 2010 at 10:11PM
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esemilio(Z5 WI)

"I am able to keep the motor running when it begins to stall by engaging the choke."

That indicates to me that it is air/fuel related. Would check for: 1)gasket leak between carbutator and intake and 2) dirty air cleaner and 3)main jet clogged.

    Bookmark   August 24, 2010 at 12:05AM
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