According to Wikipedia, Wolf said the song was inspired by watching trains in the night: "We used to sit out in the country and see the trains go by, watch the sparks come out of the smokestack. That was smokestack lightning."
Whoa, oh, stop your train
Let her, go for a ride
Why don't ya hear me cryin'?
Whoo hoo, whoo hoo
Lyrics credit to DigitalDreamDoor.