Is there a resister between coil and tach?


Active Member
May 23, 2003
Macomb, IL
I am trying to wire up the stock tach after i removed the ecu and put in a holley efi system in.

I found a diagram that showed that the tach signal was from the negative side of coil. But the diagram looks like there might be a resistor in there somewhere. If so where is it or can i put one in line?

I tried a jumper wire from coil and it made tach jump just a hair on startup and nothing after it started.

Interesting enough i tried another jumper from tach out on msd box and it seems to work. But i didnt try it long afraid of overloading something.

Tach signal is supposed to be dc square wave but i dont know voltage. The msd box puts out a 12v square wave. So im guessing it would be ok?
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