Crank no start

I have the vehicle listed above Laredo. Approximately 310,000 miles on it. 4.0 straight 6 engine. I was driving to my girlfriends house after visiting my Marine recruiter and I got out, came back, tried to start it, and bam, crank but no start. I eventually got it towed back to my house narrowed it down to the cam sensor (different name for the older cars I just don't remember the name). I put the new sensor in and it started but ran like garbage. I eventually went and bought a whole new distributor, put it in, and it still cranks but wont start. I put a new ignition coil, crank sensor, fuel filter, all new plugs and wires but still nothing. I'm getting spark and fuel (i hear the fuel filter turn on and prime itself) but it still will not turn over. I have taken the distributor out and precisely timed it about 14 times now and still nothing. On top of everything of my own mechanical knowledge and every car person I have talked to it still will not start. I heard the ECM may be an issue, but want to consult a car repair site such as this before I drop $300.00 just to be disappointed with a no start again. Thank you in advance.