magnetic trigger coil driver load req'd for signal use?

[clayb]

I took the easy way out and bought a Crane aftermarket crank trigger and
used a Pertronix points replacement kit to make my distributor into a
cam position sensor.

I suspect the Autronics SMC is not getting it's trigger signals. It does
not register any RPM while cranking, nor does it fire the ignition.
Also, it does not turn the fuel pump back on when cranking begins.

both triggers are built as ignition coil inductive drivers, and want to
switch the low side of a 12V ignition coil to ground. I simply connected
them to the signal inputs of the ECU, thinking ECU internal pull-ups
would provide the 12V part of the square wave, while the coil drivers
would switch to ground. I tried 9K external pullups, but still the ECU
didn't seem to know it was cranking. It started up with no other errors,
connected to all its sensors.

With these big transistors, do I need a high current load to get a 12V
square wave to signal the ECU? Has anyone else run into this before.
Should I use small-value resistors and more current, like 20 - 40 mA?
I'm going to try and borrow an O-scope tomorrow, so I can tell for sure.

- Clay
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