[rogerspeed]

It took me a while to find my plex instruction manual, the condenser is correct on the negative side, for the electronic tach. From what you've said the module is giving a pulse when you crank and there is power at the coil, so I don't think it's the module. The coil, I believe is specific to the system, if you have a coil with the wrong impedence it might not work? Anyway check and make sure the ground to the engine is good. Have you done this test: unplug the coil wire from the distributor, wearing heavy leather gloves and wearing rubber soled shoes hold the unplugged end 1/4" from the valve cover while someone cranks, you could run a test light in paralell with the iginition circuit, at tthe same time, to re-establish that the circuit is pulsing, if you get a spark check the cap and rotor, if you don't first try another coil-wire. One other thing, for longer life of the module, the bottom side should be slathered with di-electric tune-up grease where it mounts to the housing.

 

[rogerspeed]

I save too much stuff, the replacement module (Standard brand, Nienhoff I believe) says: "a) clean module terminals with an eraser or abrasive and b) connect and disconect the and harness several times to insure good contact."
also :" apply a liberal coating of the enclose silicone compound to the module's metal mounting plate, to prevent heat build-up."
The module I replaced had the GM # 146 1D14, I believe Marellli installed the GM modules when new. I don't know the specs on the plex, I do know if you have the wrong impedence coil on other electronic systems, it won't fire. Very specifically the Marelli installtion manual says: "An eventual check for the presence of the H.T. in the plugs by means of sparking, should be done by placing the H.T. cable end at not more than 5mm from the engine" I do not think the test light method you are using on the H.T. circuit is appropriate. There are other prohibition listed in this document. I can make a copy and mail it to you, maybe someone can scan and post.