My truck often sits for a while without use and I had the same issues. I solved it with an Airtex E8012S Universal Electric Fuel Pump. This is an inline pump, no separate parallel plumbing required. It allows pretty much unrestricted flow forward while off but prevents backflow. It is also low pressure. I have it hooked up to a push button switch- run it for a few seconds prior to starting the truck if it sat for several days and it starts immediately. I had converted to 12v. If you are 6v you may be able to find something similar. There are other similar 12v pumps too.
