The rotor spun, and it made the "whupwhupwhup" sound of a motor being turned over, but it gave no indication that it intended to start. So much for starting it on the first pull. I tugged on the rope again. And again.
... and again. It was making no pretence of trying to start, so I swallowed my pride and dug out the extension cord. It would be incapable of resisting the electric start.
[Long stretch of engine turning over and cursing omitted]
... or maybe it could. I took apart the casing and checked the spark plug. I checked the wiring. I removed and reinserted the key several times. Finally I became concerned that I might burn out the electric start, and I unplugged it again. I figured there was no harm in pulling the starter rope a few more times. I grabbed the handle and prepared to give it another pull when I spied something on the back of the motor that had somehow eluded my attention in all the time that I have owned this machine. There was a little rocker switch marked O / l -- and it was set in the "O" position. On a hunch I flicked it over to the "l" position before I pulled the rope again. To my utter lack of amazement, the machine sputtered on the first pull and started on the second.
Our snow blower has an on/off switch. Who knew? I am guessing that the repair guy must have shut it off when he was working on it this fall and just assumed that I knew it was there. Well, now I do.