I have a FAST system and I'm using an aftermarket ignition box with coil and I wired the tach signal from the box to the factory tach wire (white wire #13 in red connector at PCM) and the factory tach won't work. Is it a different signal type? Does anyone know what its looking for?
The whole car has a stock looking appearance and I don't want to add a tach and ruin it.

thanks
Rob

 

I believe the OEM tach wants a 5 volt square wave to function
properly.

What sort of signal is the FAST system producing?

You could probably buy/build a digital circuit to buffer the OEM
tach and square up any pulse/peak coming from the FAST system.

 

Is the factory tach on the Coil + or Coil - side? Also is the factory tach Pulse sensing or Current sensing?

I'm determined to get the factory tach working, just not sure how to do it?

Rob

 

I wired mine to the box and everything works fine. The ODB II computer must be different. Try contacting dakota electronics.com I believe they make a converter box for your car.

 

Yeah I just installed a Accell DFI Gen 7 with a dual sync Distributor and its a 1994 OBD1 car and the tach works with the Crane box. It must be something different with the OBD2 .


Rob

 

FINALLY I HAVE A TACH!!!
I found a little tach adapter that Crane Cams sells for there ignition boxes part number 6000-8920 only four wires to hook up and My factory tach started working.
Only thing is its a bit off I went live with my FAST and it idles correctly but its about 500rpm off when i reved it to 2000.

I'call crane tech and see what i can do.