EEC Relay...............
EEC relay closes when key is turned on, it powers coil(EDIS), fuel injectors, fuel pump relay and of course the EEC(computer).
Each fuel injector should have 12v when key is on, coil pack should have 12v when key is on.
What year is the 4.0l and it's wiring harness.
'90-'94 used an EDIS-6 (electronic distributorless ignition system) to run the spark, it was located on the rad support, front side or back side, it is often forgotten when pulling off parts.
EDIS starts spark and fuel injection when it gets a pulse signal from CKP(crank position) sensor located on the main pulley.
Without that pulse the spark and fuel will never start.
Make sure EDIS has 12v as well.
'95 and up had EDIS built into computer