240z Tach Headache with Electronic Ignition

[Lazeum]

I'm working on fixing my tach since it's not working because of Mallory ignition system (car is 72 240z with L28, mallory ignition, 3x Weber).

I've also got the tach adapter.

The tach adapter is plugged between the green distributor wire (Dist. Trigger?) and red wire (coming from the ignition - 12V when key is on "on" position).

I've tried first without bypassing the ballast resistor. Tach was working only when key was on "Start" position.

Then, I've tried to bypass the resistor, the tach is now working as it should .... but the engine does not run properlly anymore: misfire, smoke like crazy (white smoke), stalls if i release the gas pedal (even with the choke on) and backfires in carbs (3x Weber). Adapter is hot as well after 1 min. (100-110ºF).

I've decided to troubleshoot the issue by going backward. I removed the bypass of the resistance, The tach is still working very well :paranoid: whereas it was only working on "start" position before. I'm very confused! What happens? Bad connection? Why do I have 2 different results for the same setup?

Anyway, the engine still does not run as it should. Actually to bypass or not the resistor did not change anything.

It seems that the adapter is the issue on my engine running bad (bad ignition?) but it also seems to be the way to solve the tach issue.... I'm going nowhere

I've unplugged the adapter, the car works like a champ now but without tach.

What to do now??? There is a diode with the adapter, can it help? I do not know what to do. Please advice.

If I don't find any solution, I may move to the 280z tach but it bothers me to remove stock interior parts from the car (since those are the only stock parts left )

Link to a post which help me a lot with the wiring I've used.

http://www.classiczcars.com/forums/showthread.php?p=86491

[Lazeum]

Concerned by the fact that I did not understand how I can get different results with same setup, I've checked all connexions twice, cut wires to get solid contacts. It worked!

The car now run smoothly, the tach is working, no more smoke or misfire

I basically run the adapter between the white/green wire and the red wire without bypassing the resistor

I'll see how it goes, it there's an opportunity, I'll still get a 280z tach just in case (and when I have time to swap it)

I hope this can help others to fix their car. I'm learning, I'm happy

- Issue close -

[ktm]

Thank you for the follow-up.

[Lazeum]

You're welcome