1995 Other Dodge Models 95 dodge ram van

Car dies while driving, its happen intermittenly when the engine is warm, slowdown or idle ,its wont start till its cool down for an hour or two. there is no fire when i check the sparkplug[by pulling a plug wire and put a spare sparkplug and turn on the ignition ,there no spark when its touch it to the frame. I replace ignition coil, iac motor,distributor cap and rotor, spark plug and wires, egr , crank position sensor. Fuel pressure is 40 psi when i turn the key on or when engine running ,and went down to about 25psi in few minutes after engine is shutdown.There is no dtc code . Really appreciate if you can give me a clue .Thanks! John.