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Sputtering, Quitting Engine
My six-year old Craftsman mower, after being in winter storage, started up as usual and I promptly cut half of my yard's spring lawn growth. Then it sputtered out. Restarting resulted in only a brief burst of power and then immediately quitting. Only priming the engine (with the thumb-sized rubber throttle) would get it to start for these brief moments.
I purchased a "Tune Up Kit" from Sears and replaced the air filter, spark plug, and leveled off the oil level with new oil (all of which came in the 'kit,' along with an additive 'fuel stabilizer'.) For a list of Craftsman mower replaceable parts, with part numbers for this Briggs and Stratton engine, go here.
(1) MY FIRST STEP: REPLACING SIMPLE DISPOSABLE PARTS
As a matter of year-to-year maintenance, changing oil, air filters and spark plugs is important. On the Craftsman Model 917 model it's also easy and fast, requiring just screwdrivers and an appropriately sized wrench or socket for the spark plug. Take a look at this photo below showing location of the air filter and what it looks like on this specific 917 Craftsman model (called the "22 inch mulcher" on one side). The oil cap is labeled and the spark plug is obvious.
PHOTO: AIR FILTER CHANGING CRAFTSMAN 917 MOWER: Gas is mixed with oxygen for firing inside the engine. A dirty air filter makes it tough for the engine to get an adequate supply of the oxygen it needs.
But still: starting was followed immediately by the engine quitting.
Research on the internet suggested a number of possible problems: carburetor gunk build-up, fuel filter clogged, bad gasoline, no oil, serious internal engine problems.
(2) STEP TWO: EXPERIMENTING WITH A VALVE
How I solved my particular issue: I took the cosmetic plastic top off my Craftsman mower, and then I started the engine again, and kept it going (weakly) by constantly 'thumbing' gas to the engine using the primer-throttle. I noticed there is a plastic valve which opens and closes. I attempted to manipulate this valve by flicking it open, closed, holding it halfway, etc.,with the end of a screwdriver, to just see what difference it made. It made some difference but not enough to keep the engine going.
PHOTO Below: Location of the valve on the Craftsman 917 Model Mower
Water in gas?
Based upon what I was observing with the engine behavior, there was something happening between the primer, the valve, and the gasoline. So, to make certain the problem wasn't simply gas with water in it (water can condense into the container of gas due to weather changes) I retrieved my plastic oil-pan reservoir which I use for catching oil when I do an oil change on an auto, tipped the Craftsman mower sideways and poured out all the gas from the tank. I then put in new gasoline which had not been sitting for a long time (i.e., has not gone 'sour').
The mower then started as usual from the primer, ran a bit stronger than it had been, but still coughed and quit. I restarted and forced the plastic (rubber?) fuel valve to stay open using a screwdriver. The mower keep going, though not with full power. I let it die, restarted it again, and continued to hold the valve open. After a half-dozen starts-and-stops, I noticed a change: when I released the valve from being forced open, it would waver on it's own and then close, at which point the engine would then roar to full power.
PHOTO below: valve forced open on Craftsman 917 Model Mower with a Briggs and Stratton engine. I used the end of a screwdriver to push the valve open.
I had the engine quit, then I restarted the engine. It sputtered and threatened to quit: I forced the valve open again, it improved, I released the valve and it roared to normal power.
I then cut my grass, stopping about halfway through the process and restarting the engine to see if it would sputter, but instead it performed exactly as it should: whatever was in the fuel, whether water, or some kind of buildup inside the fuel line or around the valve, had been cleared.
Craftsman Lawn Mower Resource Help
Other Sources for help: Below is a You Tube Video with a basic primer on changing out disposable parts on a Craftsman Mower.
Another source of help: A good outline of how to deal with diaphragm and carburetor issues on a Craftsman mower is at the gardenweb online. large photos and well written instructions.
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