1998 Jeep grand cheerokee

My jeep was not starting very good the first time in the mornings. The fuel pump did not build pressure very good replaced that took care of the problem. Three months later same thing,changed fuel pump again but used the complete pump and filter assembly not just the pump. The pressure is much better but it doesn't hold the pressure you can watch the pressure go down in about a minute. So the question is what would be letting the pressure go down. Don't see any visable leaks, pressure regulator?