OK, try this
First, pull the connectors off the ballast resistor, the distributor, and the ECU, and "work" them in/ out a few times to scrub the terminals clean. Also feel for "tightness" in the connector
Next, hook everything up "as per normal"
Get your multimeter, and obtain some clip leads, like Radio Shack
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AN ASIDE:
It is important to understand how Mopar starting/ ignition circuits work. The ignition "switch" is in reality SEVERAL SEPARATE switches in the one container.
For start, ignition, you have:
In "run" the traditional "dark blue" run (Ma calles it "IGN1") wire is hot ONLY in run NOT in start. This supplies UNfused power to the cluster for gauges and warning lights, and goes out through the BULKHEAD CONNECTOR and supplies the regulator "I" terminal, the alternator field on 70/later cars, electric choke, if used, a couple of other things on later models and..................
THE ignition system, IE "key side" of the ballast resistor.
During start there are TWO SEPARATE circuits 'hot'.
The yellow "start" wire comes from the IGN switch, through the bulkhead, and to one of the push on terminals of the start relay. Hot ONLY in "crank", and is unfused.
The brown "bypass" (Ma calls it "IGN2") is ALSO hot ONLY in "crank", is unfused, and goes from the IGN switch, through the bulkhead, and to the COIL + side of the ballast resistor. THIS WIRE is what fires the car in "crank" because the "run" wire is COLD in "crank."
When you release the key to "run" the dark blue "run" wire is HOT and the brown goes COLD
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SO
First clip your meter up to the dark blue "run" wire and ground. You can access this at the "key side" of the ballast, or hook it to the blue field wire on your alternator. Turn the key to "run" and observe the voltage.
A BETTER WAY is to hook one probe of your meter to the alternator blue field wire, and hook the other probe to the battery POSITIVE post, and read the voltage in "run."
WHAT you are measuring in this last hookup is the VOLTAGE DROP in the ignition harness. The circuit path goes from:
battery -- fuse link -- through the bulkhead -- ammeter circuit -- ignition switch connector -- through the switch -- back out the switch connector (dark blue) -- back out the bulkhead connector -- to the "key" side of the ballast
You are HOPING for a VERY low reading. Anything OVER .2--.3V (3 tenths of a volt) means there is unacceptable drop in the above circuit path
Your top suspects are the bulkhead connector, the ignition switch connector, and the switch itself, and last, the ammeter circuit.
NEXT test the brown bypass circuit. Again, with everything hooked up "normal" move your meter lead from the alternator field to the coil + terminal. Leave the other lead hooked to the battery POS post.
Crank the engine USING THE KEY, NOT by jumpering the start relay
Once again, you should only read a few tenths of a volt.
If both these above checks are OK, you should be getting "OK" ignition voltage from the battery
Next, pull apart the distributor connector and hook your meter to the distributor on low AC volts. Crank over the engine. The distributor pickup should generate about 1V AC. Pull the cap and inspect the reluctor and pickup for rust, debri, chips, damage.
Buy yourself the proper .008" (that's inches not mm) brass feeler and check the reluctor gap. Last time I was in O'Reallys they had them.
Next, "rig" a clip lead to ground and hold it near the top of the coil tower with the coil wire removed. Have someone operate the key and see if you get a nice fat spark. If so, you are OK to this point.
If not, I'd take a good hard look at the wiring. Here are the simplified diagrams for the older "5 pin" ECU and the newer "4 pin" ECU
http://www.mymopar.com/downloads/Ignition_System_5pin.jpg
http://www.mymopar.com/downloads/Ignition_System_4pin.jpg
Following the layout of the connectors, you should be able to "ohm" out the wires to make sure you have continuity.
