[Tommy]

Tom,
I'm not sure the following explanation will work for your problem, but it happened to me and is worth considering.

I was running an electric fuel pump with a regulator built into the pump (Holley Red). That system regulates pressure with a spring controlled valve on the output side of the pump. When pressure in the output line exceeded the factory set 7 PSI, the valve would dump excess fuel back to the input side of the pump. Thus, when the fuel being pumped exceeded demand, a small amount of fuel would circulate continuously at the top of the pump, all the while absorbing heat from the pump. On a hot day, the combination of ambient heat and heat from the fuel pump would vaporize the fuel circulating above the pump and cause a vapor lock. It happened to me during a track day event, and I solved it temporarily by packing the fuel pump in ice. That is also a way to diagnose the problem. I solved the problem permanently by installing an unregulated pump and a separate regulator downstream from the pump. This regulator routes excess fuel back to the fuel tank.