On the back of the machine there's an aluminum cover. Inside that cover is a graphite rotor with 4 graphite vanes. You turn on the power, the motor spins the rotor, the rotor draws a vacuum from the fuel tank and pumps it to the nozzle. A few seconds later, the ignitor sparks and a flame is born. If the flame is good, the photo cell tells the machine to keep running. Bad or no flame, and the motor shuts off. The graphite rotors are fragile and shatter easily, from dropping the machine or what not. If a vane is stuck or the rotors broken, you won't get an adequate fuel supply and the machine probably won't ignite.