I have used electronic solenoid valves for propane metering and they actually work very well. I have a semi-auto combustion and a full-auto is in development. I need to get that damn thing finished, er, started... hah!
Oh, and there is no such thing as a pneumatic solenoid. A solenoid is a coil of wire around a rod that pushes it one way or the other depending on the direction of current.
Question about valves
<a href="http://www.launchpotatoes.com"><img src="http://www.launchpotatoes.com/images/up ... 2.PNG"></a>
http://www.LaunchPotatoes.com
http://www.LaunchPotatoes.com