[ubnjtx]

Craftsman model 917.276621 21.0 HP single cylinder Kohler engine. After running the tractor for around 10 minutes, it stopped and my son thought it ran out of gas. He filled the tank halfway and tried to start it. The engine would crank over steadily, but not start. No adjustment to the throttle helped. Took off the cover and pulled the plug. Plug was dirty, so I cleaned it then put it back in. Still would not start. Pulled it again and cranked it over to see if there was a spark, but unable to see one at this time.No other known problem at this time. Any ideas.

[Elvandil]

You'll need to find out if it has a spark. If it was stored outdoors, look in the gas tank with a flashlight and see if there is a bubble of water floating around in the bottom.

[Drabdr]

How old is the gas in the tractor? maybe it has some old gas in it, which is giving it trouble.

[ubnjtx]

Unable to get a spark as previously noted, gas added from storage container may be several months old but worked fine in weed trimmer. Sprayed engine start in carb with no results.

[ubnjtx]

Oh, Also stored in shed, not outside

[sixpack]

The craftsman tractors usually have two switches which can affect the spark, one is located in conjunction with the parking brake and the other is located under the seat. The one under the seat disables the motor if the blade is engaged and the driver gets up from the seat (safety feature) same with the parking brake (no start unless seated on vehicle). If these are functioning correctly and you still have no spark your stator under the flywheel is probable defective. Have you tried a different plug?

[ubnjtx]

Tried a different plug, but didn't actually check he switches just sat in the seat and tried to start as usual will do tomorrow. next will check the stator. Thanks.

[Elvandil]

Check for a spark without a plug. It's often easier to see than it is in the gap (or you can hear it).

If no spark, it could be anything from the coil to the points, to anything in between.

[Knotbored]

If the gas is "several months old" I would bet its moisture (water) in the gas tank.
USA gasoline contains 10% ethanol which absorbs moisture far faster then gasoline in the olden days. The water puddles in the bottom of storage containers so gas into weed eaters from top of tank may work fine, bottom of tank may be poluted.
Drain all the gas off into clear container and look for water in the bottom (it will be quite obvious.)
Quite often I find such water in chainsaw and weed eaters stored inside, I live in forested area so I can safely burn off that 1/4" of poluted fuel.

[wowzer]

Sure sounds like bad gas/water to me.

If it ran for ten minutes and then died I doubt it's any of the switches described.

Was the "different plug" you tried a new one?

How did you test the plug? Take it out then connect it to the wire and ground it out and turn the engine over?

[ubnjtx]

To Wowzer: Affirmative, new plug, no spark even without plug (used screwdriver to ground) No water in gas, drained it out. Changed out fuse (20A) although old one appeared fine. It's getting gas. Changed the filter (again, appeared fine) new Air filter also. Cranks over fine, just will not go. New gas/No Go. Not sure how to check the out all the safety overides (switches) Thanks

[Koot]

There's one thing I can guarantee - it ain't gonna fire-up without spark! So all the talk about anything other than SPARK (bad gas, filters, etc.) is fruitless when there's NO FIRE to ignite the fuel mixture!

Check the seat switch and the two interlock switches. Also, check the ignition switch and the 20 Amp fuse. Finally, make sure all the wiring harness plugs are plugged in securely.

Question: Are you sitting on (occupying) the seat (or have a heavy weight in the seat to depress the seat switch) when you are testing to see if you have spark? Just asking!

[ubnjtx]

Thanks for all the input, Yes, sitting on seat, brake depressed, throttle open, not on choke, getting fuel, ??

[ubnjtx]

Also, new fuse, still have to check all connections though

[sixpack]

ubnjitx,
You need to check the switches I mentioned, the one under the seat can be bypassed usually with a paper clip, same with the other one. I take it you don't have a PTO on the tractor so thats one less sw to worry about. These sw's are just NC or NO style, if these check out okay then your problem is more than likely in the Mag/CDI unit, these are located under the flywheel. To tackle these you need a puller and a digital meter plus some know how and a schematic would be a great help if your not comfortable with electronics. Maybe one of your friends who knows about gas engines could give you a hand. Wish you lots of luck in your venture.