I changed the fuel pump and fuel filter and it starts but then dies after about 5 seconds. I have to wait a couple hours then I can try it again but it’s the same thing... any ideas ? Maybe fuel pressure regulator ?

its a 96 with a 302 5.0

 

Why? To what (brand, PN, source)? Did the replacement pump pass the same test that the original pump failed? Do you still have the original pump?Why can't you try to restart it immediately?Are you guessing, or did you do some diagnosis that led you to the FPR?Put that AND all the truck's other details into your signature as this caption explains:

(phone app link)