Join Date: Jun 2001
Location: Jefferson, Georgia.
Are you sure the pump is continuing to run? It sounds like the pump may be getting hot, overheating, and once its had time to cool you can go until it overheats. Iíve been down this road, I didnít realize at first the pump was shutting down.
A return line using a return pressure regulator and fuel log (the line at the carb connecting to both fuel bowls) designed for the return line could be one solution. Allowing the pump to circulate fuel helps keep the pump cool. Barry Grant used to have this information and design options on his web site, not sure if Barry Grant is still in business but you might search for it.
Youíve done a number of good things, but given the bowl is dry Iím rather confident that your pump is overheating. Air simply canít keep fuel from flowing in, it may displace some fuel as it flows, but an electric pump is going to fill the bowl especially if itís allowed to run a few seconds after the motor stalls. Boiling fuel and vapor lock on a mechanical pump design are a different animal when you convert to an electric pump.
Also, your cap should vent the tank, youíd never want to obstruct venting the tank since that too would cause a vacuum for the pump to work against. Things have changed with modern cars and the fuel system design has changed such that there are better controls for allowing air to displace fuel, but your design needs air and thus there will never be a hiss.
Good luck with it, Iíll poke around too and see if I can find the Barry Grant return line info.