A solenoid-operated liquid spray gun having a lightweight, corrosion resistant plastic housing which enables the spray gun to be mounted on and be more easily moved by robotic transfer devices. To effect the necessary flux loop within the plastic-housed spray gun for reciprocating a valve plunger in response to energization of the solenoid coil, the spray gun includes a radially disposed flux-directing member adjacent at least one end of the coil. The flux-directing member, while extending radially outwardly a distance less than the diameter of solenoid coil, effects efficient flux direction for operating the solenoid notwithstanding the lack of a magnetic conductive medium provided by the metal housing of conventional solenoid-operated spray guns.