Aftermarket tach cant read ecu tach output?

[blues14]

I bought a splitfire 5" tach off my buddy. i wired it all up and connected green wire to pinout #7 off my ecu harness and .....Nothing. so i thought maybe it was bad. hooked it up on my 86 ranger and it works perfect. are there some tachs that cant read the rb's because of the ignitions setup? cuz the needle doesnt even flinch. does anybody know of a brand or type of tach that will read the signal? or even better make the stock tach work accurately?

[Slo_240sx]

Aftermarket tachs have little wires on the back you have to cut to make the signal work properly. But since youres doesn't work at all I say you need a tach adapter. Call the company they can supply you with one.-Alex