Fuel issues which no one can figure out...

[Stoutstanding]

Hello all,
First time posting to this website. I have a 1972 GMC sierra grande 2500 that I have fuel delivery problems with. I keep losing prime on the inlet side of my pump. The truck has a 1997 454 with an Edelbrock electric fuel pump located on the passenger side frame (beneath the tank). Here is the series of events that led to my problem: My gas cap was loose and spilled fuel so I replaced it with a new vented cap. After driving it for a couple miles I vapor locked the system. I unscrewed the cap, relieved the vacuum and reprimed the pump. Since then, I have had constant issues with my pump loosing prime on the inlet side. I thought I may have ruined the pump, so I got a new one from Summit. That didn't help. I then decided to change all the rubber hoses and filters in case they were the issue. I also checked the sending unit, the lines, sock filter and tank to make sure it was clean and had no air leaks. Everything checked out fine. Tried driving it, but lost prime again and had to siphon the line to get fuel. I have talked to mechanics and done extensive research, but I have no idea what is causing this. My tank is in the cab, behind the seat. The sending unit goes through the cab floor, attached to a rubber hose, then the 100 micron filter, rubber hose, pump inlet. There is no return line nor a vapor line on the truck. The outlet side of the pump goes to the a filter then the carb. If anyone has any experience with this type of issue please let me know, I am at wits end! Thank you very much.
Chris
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