No power to coil - even after jumping ignition switch

[Surfbeamer]

Hi again, another electrical mystery, at least for me.

I have a 1975 spider, it ran about 4 months ago but had a blown head gasket so I replaced the engine with a 1978 and am just going through the start up.

The engine turns over (starter works, lights work, ground seems fine), mechanical fuel pump is ok, but no spark from coil. With the ignition switch in run position, I have no power at the coil (+) terminal (the blue/black wire). Per the wiring diagram, the blue/black wire runs directly to the ignition switch. With key in run position, the pink and blue/black wire (they are joined into one spade connector to terminal 15 on the ignition switch) connects to the black wire. I checked the ignition switch terminals. The black and brown wires have about 13V. These come direct from starter where the primary battery cable is connected. I tested the brown and black wire terminals coming from the starter and see 13V, no surprise. Here is the weird thing: I jumped the live black to the pink and blue/black wire connector on the ignition switch. The volts then drop to zero, and no volts at coil. So before connecting i get 13V at the igntion switch black wire. After connecting, it is zero. Then i connected the ignition switch brown wire (the other ignition wire with 13V ) to the pink and blue/black wire connector. I see sparks, dash lights come on, and there is 13V at the coil (+) therminal.

So Im puzzled. Why do the volts go to zero.

Just to be sure, I added more grounds to engine and chasis, although i didnt think that would help. The alternator on the 78 is on the opposite side, originally i added a jump wire between alternator and starter and just isolated the original wires on the other side. Then I removed the alternator to starter jump wire and ran an extra wire from the original alternator to the new alternator. No effect.

I also tested the resistance of the coil, resistance from (+) to (-) is about 3.5 ohms and from the + to the High Tension HT wire is about 8000 ohms. These were a bit off spec. I tested another spare coil with similar numbers, both coils worked 4 months ago. I dont think they have both gone bad and would affect volts at the coil.

Any help or suggests on what could cause the drop in volts at the ignition are greatly appreciated.

Cheers

[Surfbeamer]

To follow up. I found the ring connectors on the 3 black wires from alternator had high resistance. Even though they were clean and shiny to the eye. I steel wooled them and then I got 12.5 volts to the coil. I have decided to go through entire wiring system to clean contacts as poor connections seems to be the root of most spider electrical issues.

I also noticed that the car runs differnt depending on how I jumped the black leads over to the alternator. So I will pull the original wires out from the right side of engine and reroute to the left side where the alternator is now, rather tha adding a fat cable.