The pictured vapor-liquid separator, original Chrysler part number 3642105, houses the four vapor vent lines from the fuel tank mounted internally as stand pipes to allow the vapor entry and liquid fuel separation in the housing. One tube inside the separator does not extend as far into the separator as the other three. The lower tube is the liquid return line to the tank as well as a vapor tube. These four tubes are essentially open and can pass air. The following images shows schematically the inlet tube arrangement:
View attachment 154725
The separator outlet tube has a brass check valve, called the overfill limiting valve, that connects to the vent line leading to the charcoal canister. The check valve is closed until vapor pressure reaches ~0.5psi. At this pressure point the check valve begins to be pushed up and vapors travel to the charcoal canister to be purged into the carburetor when the engine is running. The following diagram illustrates the check valve assembly:
The tube and valve can pass air outward from the separator, but should block air going into the separator. If the valve moves when the separator is shaken, it is free and should function as intended. The flap-like sound heard when pulling air from the outlet tube sounds like the valve is moving.
The pictured unit appears to possibly be new (originals were galvanized), or refurbished, but if the valve is stuck with fuel varnish or moderate dirt, cleaning by submerging in a solvent such as carburetor cleaner (old Berryman B-12 is ideal) can remove the varnish. Agitating the unit in the solvent can help free up the valve.
If the unit is rusted, or the valve is otherwise stuck, it may not be possible to clean it up. Cutting open the unit for manual cleaning, followed by resealing it is possible. Chrysler service instruction for an inline valve that could not be freed was to cut the tube out and splice in a replacement tube/check valve (part number 3642263). Unfortunately, 3642263 has been long discontinued.
The following diagram illustrates the overall Vapor Saver system, part of the Evaporative Control System (ECS):
