starrting problems

I have a 02 dodge ram 1500 with the 5.9l, I bought it used. ever since then its been hard to crank. you turn the key and it turns over for almost a minute before it fires up. I have replaced every sensor on the motor and the computer.
I need to get it fixed cause in April ill be driving it to South Carolina and don't want any problems, Thanks in advance

Is the Check Engine light on?
Do you know how much fuel pressure you have?

no check engine light, when I had problems with the computer I had 52psi but it would drop back to zero a few seconds after you stopped trying to crank it. Ill recheck tomorrow but it runs and I have been driving it.

sorry its been so long, it has no pressure after sitting awhile and 50psi after the key is turned a few times. I don't have a clue I'm guessing fuel pump. is the pressure supposed to drop down when off?

(5) Start engine and bring to normal operating
temperature.
(6) Observe test gauge. Normal operating pressure
should be 339 kPa +/–34 kPa (49.2 psi +/–5 psi).
(7) Shut engine off.
(8) Pressure should not fall below 30 psi for five
minutes.