Vapor Separator & Canister
 

Have a '73 that is got me a little puzzled. When I filled up with gas, up to the bottom of the tube that extends down into the tank, last week I noticed a 3 foot diameter puddle of raw gasoline coming from the vapor canister behind the left front wheel. I was sitting on fairly level ground...maybe a slight left side lower for water drainage on the concrete pad at the station.

Got out the assembly manual and looked at the system. Seems there is a vapor separator, part number 7028035 on the left top side of the fuel tank with rubber hoses from the tank to the separator then to a steel line that goes along the frame and into the vapor canister. I looked at the installed vapor separator and it is intact, no cracks, etc.

Was wondering if the vapor separator, which I believe has a foating type check valve may be malfunctioning. Also, since the parts are all original, the vapor canister purge valve could also be ineffective. Anyone seen this problem and what resolution did you use?

My thoughts are to replace the vapor canister assembly (still available through GM) and take off the vapor separator and see if it is functioning correctly, but don't know how to check its functionality. Anybody know how?

Could this also be causing poor mileage, by sucking some raw gas off of the tank through the vapor canister and into the manifold? I have a 350 bored over .030 with a 268H cam. I am getting about 9 to 10 MPG babying it. I would think it should get around 15 MPG!

Any help would be appreciated!:)