What we found was there is power on DLC 16; have NOT checked the two ground ports yet (#4, #5) Wasn't aware to check that until I read the copy of this post that Al sent me.
Check the connector grounds as well.
There is spark on the coil going into the distributer but NO spark coming out of the distributer to the spark plugs
Installed a new distributer cap, a new rotor and a new module inside called an ignition pickup module and still no joy
Check the coil connector if there is +12V going into it, dark green/ orange is power feed and grey/ white is ground.
Check coil primary and secondary resistance to see if coil is good; primary should be about 1ohm, secondary ~11-15kohm.
Check if the coil output spark wire gives good spark - test on known good ground point to block when someone is cranking.
If coil is good and it gives proper strong spark, you should have spark from the secondary spark wires to plugs if the distributor cap & rotor are good.
The Ignition Pickup Module has a plug on it that has three wires in it and I don't know what they do or where they go because I don't have a wiring diagram for the 98 Jeep Grand Cherokee Limited 5.2 yet
The plastic plate with the plug in it is the cam position sensor; what it actually does is it provides PCM with the information when to fire the injectors and when to shut them off.
Distributor alignment is VERY important on these for the fuel sync to be correct. With the #1 at TDC, distributor rotor should be aligned with the slot in the cam sensor plate. If not, rotate engine once full turn and check again.
Cam sensor has three wires; one is giving +5V sensor feed, one is ground and one is sensor output. White/ black is feed, black/light blue is ground, grey/black is signal.
Further, the question is are those HARD Grounds or ELECTRONIC Grounds from the PCM?
I highly suggest getting a factory service manual (FSM) if you don't have one, it is essential for diagnosing things like this. There are both hard grounds to chassis/ battery, and there are PCM- controlled grounds.
Sensor +5V is fed through PCM, most 12V feeds come from the PDC (direct fused feed or through the ASD relay).
Spark timing is fully controlled by the PCM, ignition coil is ground controlled.
Fuel injector pulse width/ timing is PCM controlled on the ground circuit.
Quite a few other things are ground controlled as well.