Go back to post #22, Notice how the fuel filter is oriented with the nipple up. Any air or fuel vapor in the line,will take the path of least resistance, and scramble up that nipple as fast as it can. And it will be driven back to the tank by liquid fuel following. When you shut the engine off, and the pressure relaxes, then any fuel boiling between the pump and the filter, will send the vapors out the return line.While there may or may not be vaporous gas in the short tube from the filter to the carb, this is easily dealt with. Further more as the fuel cools in the line, it will condense back into a liquid state.The mechanical pump will fill the remaining portion of the line in a few engine revolutions.
