The way a propane system works is somewhat close to whatnyou describdes....it comes out of the tank in a high PSI liquid form and goes thru either a solenoid or vacuum safetynshut off then goes to the vaporizor....the vaporizor usually has engine coolant running theu it,some sit in a cooling jacket in the engine,the liquid heats up and vaporizes to gas and gets its psi resuced down to usually around 1-5 psi and goes to the air fuel mixer where it goes into the engine.
Being that it is a highly flammable sytem it is best if tou have amprofessional look and work on the sytem....anything done wrong could create a huge fire and possible property and personal injury.