Mike,

Do you have the propane solonoid that has a little red LED on the top of it? If so, are you seeing the red light when you initiate the start sequence? You might want to reverse the lines on your solonoid to see if you can unstick it. There might be something stuck in it that is preventing it from opening? I had one that stuck part way open so even with the system powered off, i could hear start gas leaking into the engine. If you are not getting the red light at all, then i would check the connection between the solonoid and the ECU like you already mentioned. Just another thought.