Tach signal wire HELP

[Fire604]

To all the electric gurus, I need a pulsed negative for my Speedhut tach. Can I tap the #4 pin at the ECU to achieve what I need? Is this a reasonable solution? Suggestions?

I have the FSM and a color schematic of the electrical system but reading an electrical diagram is not my strong suit. Well, ok, I'm a wiring theory moron but more than capable of soldering and heat shrinking.

Thanks!

'78 280z

[Zed Head]

The stock tach uses the blue wire from coil negative. Won't that one work? Not sure what you mean by "pulsed negative". Why do you think that pin 4 would work?

[FastWoman]

Pin 1 is the signal from the negative side of the coil.