primering the gas pump

[willy3486]

I am stumped on my truck. It is a 1970 c10 with a 307. It has a mechanical gas pump mounted on the engine. The truck sat for a few years but was in a covered building. I put in about 2 to 3 gallons of gas in the tank. I put new rubber gas hoses on it. What I wanted to do is I put a fuel filter in just before the pump temporary so that it can collect any rust as I clean the lines. I then took the line out of the pump that goes to the carb and put a hose on that line just before the carb to run into a old gas can to collect it. I wanted to do this and run a gallon or so of gas out to clean the lines. When it turns over I can see gas in the filter move but the filter dues not fill up. Am I doing this wrong or what can I do to it to get it primered so to speak so the gas will run in the old can. I don't think the lines are clogged because I drained the lines when I put the new lines.