'94 4.0l will use an EDIS-6 module for spark
Usually located on the Rad support, my '94 has it on the grill side of rad support, and drivers side of rad support.
I have seen these damaged from front end collisions and then give intermittent issues because they were not replaced.
EDIS module connects directly to the CKP sensor and directly to the coil, it runs the spark, with or without computer(EEC, PCM) input, this input is for better spark advance but is not required for engine to operate.
Coil pack gets 12v when key is on, other 3 wires are grounds controlled by EDIS module.
There are 3 separate coils inside the coil pack, they share the 12v only.
A coil is a transformer so there would not be 12v at the spark plug wire connections when key is on, there is no power connection between Primary coil(12v) and secondary coil(spark plug wire), they do share a ground so can be tested with OHM meter.
Google: How to Check an Ignition Coil Pack the easy way
it is a youtube video
This is a good page for EDIS module info:
http://www.dainst.com/info/edis/edis.html
You could ohm the wires to check for shorts or breaks
I have never come across an intermittent CKP sensor, dead yes, but not intermittent.
Do you have no spark at all or do you get some spark?
On rare occasions I have read that the woodruff key failed on main pulley so CKP signal didn't match actual TDC, but you would still get a good spark just not at the right time