I think because the zex box is tapped into the vacuum line for the throttle some of it may be coming through that way. leave the nozzle out, arm it, point the nozzle away from your face, and then reach down and roll the throttle pulley and make the car got WOT, you should trigger the solenoid. and it should spray. make sure you're holding it tight though, it does come out with a bit of force.