91 Plymouth voyager melted coil pack replaced it, melted another one, replaced it, now no spark
That's terrible, seems like time to run pinpoint tests is in order. Perhaps the melted ones were shorted internally, but the latest one could have an open circuit. Now you need the ohm specs for the coil pack, and to have the power, ground etc and the inputs and outputs for the DIS module. Time to seek a service manual at the public library. I get mine at the city library, because dealers have donated factory manuals there. Automotive databases can have this kind of testing, and the TSB list is worth a review. A mitchell database usually has what you want. The chilton one has been just enough info to get me pissed. Happy research.
A haynes manual can be borrowed for free at the county library perhaps. and a meter can be had as well as a test light, pretty cheap at the parts store. You need to check with things disconnected, is the harness ok ? Is each component open or shorted to ground or shorted to another circuit. Time for the head scratchin to begin.
Being you have a plymouth, there's a chance the DIS is in the ECU or the main brain. You may want to check the schematic for correctness by seeing if you have dealer updates in the automotive database. That tidbit would have saved me a few weeks if I had it for the last mopile I fixed.