It's a 6 liter gas motor with eight thousand miles on it fresh rebuild the crank

New fuel lock out module crank senser new cam senser but engine dies and wont start for 15 min cranks but wont start i have 60 lbs of fuel pressure at the rail ....could the ecm be going bad???

sir: sounds like a passlock II issue, is the security lamp flashing when you crank the engine ?

No security light,i just put a a/c delco crank sensor in it runs good and is thowing a code po300 which is random misfire ,do i need to get the new sensor flashed so it wont throw a code? I changed the pig tail at the crank sencer also it dont stall anymore but throws the misfire code!!!! It is driving me to drink..lol

Missfire causes: Low compression, Valve clearance, valve spring, vacuum leak, fuel injector, low fuel pressure, spark plug, ignition coil, injector wiring harness, coil wiring harness, ECM.

The motor was just rebuilt it has 8 k miles,i did some welding and grinding on the truck and the ecm was shocked but it did reset after 12 hrs i am gonna get it put on a computer today to see ,i hope its just the ecm i can get one and have it flashed for under 250. Thanks for your input I really appreciate it