As the title says, I'm trying to get my stock tach working on a monster project of someone else's that I purchased. I've got an aftermarket tach working, as its hooked up to the wire from pin 4. But when I hook up that wire to the blue/yellow wire at the igniter via a jumper wire, the stock tach does nothing. And if the am tach is touching that jumper wire, it stops too. But if the jumper is there, and I hook up the am tach later down the line, it still works (but the stock tach never does). Any ideas? Maybe that blue/yellow is the wrong one? But from everything I've read it's the one that runs to the stock tach. Any help would be appreciated!

93 Miata
93 5.0
A9L ECU

 

Woohoo! Figured it out. Apparently the wiper motor wire (which is the same blue/yellow and in a similar location) isn't the one you want to splice into.