I believe it's a spring loaded valve with an electromagnet used to pull it open. All that plumbing should be inside the sealed and vented propane locker.

Max, I have a propane sensor purchased from an RV supply that is wired to come on with the solenoid circuit. I get a momentary chirp when I turn it off so I assume it's still good but I suppose I should check it with an unlit propane torch or something.