Using Coilx with my Festiva

[jemartin144]

I thought I would post this in case anyone else was having a similar issue as I was experiencing with my carbureted Ford Festiva. I am setting up the datalogger with a Coilx to record the RPM. I am hooking it up to a Gr/Y wire that comes off of the negative side of the Coil and is labeled the RPM signal wire. Tried hooking it up with the coilx and got no signal. Put a scope on it and noticed the the voltages generally peaked at 73volts.



So, reading around I noticed that an earlier version of the coilx used a 24v zener doide instead of a 75v one, so I decided to give it a shot. Soldered on a .5w 24v zener in parallel with the 75v zener and voila it worked!



Now, after I did this I realized that this could possibly mean the my ignition coil is getting weak or something is wrong with it. I don't know if that's how it works or not with ignition coils. I plan on trying another one sometime in the near future.