Check for spark. If no spark suspect coil(s), crank or cam sensor, (I think they'll still run without a cam sensor, but I can't recall), or it could be the ignition module. I believe the 93 year was one of the last before ignition module was integrated into the PCM.
Can you hear the fuel pump run when you turn the key to "ON"? If it runs, does it give proper pressure? I don't know for certain what the 4.0's need, but I imagine it's 30 PSI or higher.
Thats what you should check first, I think.