So o have been thru many things on my Durango..
I have replaced the following to track it down and several parts helps but not cured said issue.
New distributor cam sensor inside that, new crank position sensor, fuel pump, plugs,wires,oil pressure sending unit, and a tps..
I am at loss for understanding what else it could be.. I have checked fuel pressure and leak down.... Nothing... Oil pressure is immediate 1-2 second crank it's already about 30psi, all sensors I can look at on the scanner but nothing is telling me what causes 8-12 second crank before it fires up....
I also replaced the auto kill relay...
Any help would be great

 

i know you replaced the fuel pump, but bear with me.

have you tried priming the fuel system before cranking? (turn key on, let fuel pump prime, turn key off, turn key on, pump prime start)

if that alleviates the issue the check valve in your pump in s bad (iv seen crazier things than a bad check valve out of the box)