A quick inspection revealed a trail of rapidly evaporating gasoline back towards my house and a growing puddle of gas under the car.
Turned out that I had forgotten to close the carb bowl drain valve after parking the car the last time (I always shut off the fuel feed and drain the carb bowl after every drive). I'm surprised that I didn't notice the gusher while the car was idling in the garage!
I never realized how many turns it takes to close that valve until I had gas gushing out of it and all over my arm while I was trying to close it.
