What cause low fuel pressure in a 1994 dodge ram 1500 5.l?

Evidently you mean the 5.2Liter, The 1994 Dode Ram 1500 offered a 3.9L, 5.2L and rare but did exist was the monster 8.0L, 488 cubic inch, V10. Anyway could be a bad fuel pump, clogged filter, fuel pressure regulator. The spec for the 5.2 is 40psi at rail, ± 5psi.