Gas Delivery Problem

[Cris]

I have a very stock 63 C10 with a 230 inline six. It runs perfect until the gas tank gets below 1/4 tank. Then, many times, it will not start. Especially if the truck has been sitting for a week or two. The fix is always the same. Cup my hands around the fuel filler neck and blow (pressurize the tank) for a few seconds and/or add some fuel directly down the carb.

I am guessing the fuel pump (stock mechanical) is dry and cannot suck gas in without some help. If the tank is full enough, this is never an issue presumably because the gas is higher in the tank (behind seat tank) and gives enough pressure.

Anyone dealt with this before? I'm getting tired of giving my truck a blow job to get started........

Thanks, Cris