Engine/Transmission (1998.5 - 2002) Ecm?

[KCanepari]

Truck died the other day. noticed Fuel pressure had been running 2 psi less than when pump (stock) was new almost two year ago. Replaced pump. Had a very hard time priming system. First time I bumped starter went right up to 13 psi. then nothing. got a bunch of codes one of them being "no signal between ecm and injection pump" . I cleared the codes and then got the pump to run a couple times and got the truck running. pressure stays steady at 13 psi. the problem is sometimes when I first turn the key on it pressure goes right up, then the next time nothing (verified no sound from lift pump) The truck will still start and pressure comes up once running. I've thought about making my own relay, but am worried pump will not run for 25 seconds after key is off like stock.