Stock tach and distributor. The back of the tach has a green and black wire screwed onto a two post terminal toward the top of the tach. A third, red/white, wire on a single plug in post towards the middle of the tach.
Engine compartment tach wire is blue. If I connect the blue tach wire to the negative post of the coil I get no fire from the coil. If I disconnect it, the engine fires up immediately. The car has a transistorized ignition module mounted under the dash. I believe there is, but have not actually seen, a resistor from the module to the blue tach wire.
I hope this is enough info to allow someone to come up with some suggestions.
I have a spare stock tach that could be hooked up externally, if I knew how, to make sure the one in the car will work properly.
Thanks in advance for any and all help!