mine didnt work when i bought my truck. the pump did not work at all, ignition unit buzzed but no spark and i was not sure what the nozzle was like. I replaced the pump and new spark plug and now it works. It was down to 20 degrees here the other night and i started it up just for fun.... while cranking the truck and bumping the flame heater, i still cant tell really if its working or the truck starts by itself. maybe tonight ill try starting it without it just for kicks and tomorrow night ill start it trying to use the flame heater and see what happens. i know it works though because after i shut down the truck, i turn the ignition back on and bump the switch a couple times, i can hear the "woof" of the fuel igniting in the manifold..... so does that mean it works in cold weather while cranking?.... thats a question for somebody more experienced them than me.