there are two things to look at
first is the fuel lock solenoid, that opens flow from the tank into the filter and/or evaporator(converter).
Now some LP systems have a vacuum hose running to a filter assy that is hooked inline with the converter, in this case there is probably no lock-off solenoid because the filter is actually the fuel lock valve and opens when the engine pulls a vacuum on it.
secondly there is a diaphragm in the mixer (carb) that also has a shut off (bullet valve) on it.
If you hear it rushing into the mixer (carb) then the mixer diaphragm is probably bad and should be replaced.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.