Tach doesnt work

[grantman240z]

the tach on my 72 240z just doesnt work. the guy who owned it before me had put in a 280zx 5-speed and electronic ignition, i think it has something to do with the transmission. unfortunately, the previous owner was not very thorough in some of his work and decided not to fix the problem. he said it was something about a resistor or some other crap, but it looks like there is a tach output from the distributor cap that isnt connected to anything whatsoever. i dont really need the tach, i just would like to have it working.

[2ManyZs]

You will probably have to tell what type of electronic ignition is in the car, there are so many different ones and they usually feed the tach differently. Perhaps if you post that, someone with the same set-up may be able to help.

[Royce]

It is not the transmission. 2manyZ's is right you it has to do with the ignition. They are all a little different so first you would have to identify the tach lead from the particular type of ignition that you have. You won't be able to get the the stock 240Z tach to work with an electronic ignition signal. From what I have read even the 260Z tach which is for electronic ignition won't work with aftermarket or later Z or ZX electronic ignition systems. What is commonly done is to take apart the 240Z tach and put 280Z tach guts into the 240Z tach housing, so you can use the same gauge face with the higher redline, and then put it back in. I don't have the technical specifications readily available but I have a writeup somewhere and will look for it and post when I can.

I sold one 280Z tach for this purpose a long time ago. I just got another one that I am going to hang onto for just this reason.

[AxtellZ]

I didn't check before this post, but i'm fairly sure Carl posted a tech write-up on this at Zhome.com

You may check there if you haven't. I've read also that folks at MSA and at Crane can hook you up, assuming it's one of their products. Good luck, Jeremiah

[grantman240z]

the guy said its a 280zx electronic ignition...but i would have to verify that after my car gets out of the shop.

[2ManyZs]

I'm not sure but it seems to me I've seen cars with the original tachs hooked up to the ZX electronic ignition. I may be wrong, and I haven't tried it yet, so do some research.

I know that MSD's and a lot of the other aftermarket ignition systems aren't compatible or you need to buy an adapter (MSD anyway) so do some checking.

As a side note, I have a car with the MSD and an aftermarket tach ( race car) that the tach works just fine. This was after everyone told the guy that owned it he had to have the MSD trigger to hook up the tach. So a little experimentation might pay off!

[Royce]

Sure, I agree that anything can be made to work with the right amount of time and money. I don't think the stock 240Z tach will work with a Datsun/Nissan electronic ignition, or aftermarket either, without some type of converter or adapter. I think that using the 280Z tach modification is tried and true and allows you to keep a stock look. It is actually a quite common switch from what I hear.

There is some write-ups at zhome.com in the Z Techical Library under Index of Technical Articles in the Ignitions Systems section.

Also, good distributor & ignition stuff at http://www.geocities.com/zgarage2001/z.html under the Performance Tips heading.

(don't remember if he discusses the tach switch or not).

I wish I could find the article that Pete Sanders wrote to the internet Z club a while back. It is on my home computer which has taken a turn for the worse recently! No virus, I believe this problem is between the chair and the keyboard!

Have fun!

[Royce]

I am not too proud to not admit it when I am wrong. Sometimes you have to be proven wrong to learn something new!

I have just been corrected on the tach issue during a different Z conversation. I am going to try to get the details and post them under technical articles.

Stay tunned...

[2ManyZs]

I hope you let us know, I will need to know how it is done when I get the motor back in my 71.

BTW Royce, I had my faux-pas with the LSD slip-up the other day, so none of us are perfect. Darn it!!

I knew I had heard it could be done, but unfortunately I have never seen or heard exactly how it is done. Unless I want to go through the old try it and if it doesn't work, try something else.

[EScanlon]

I have a 71 240 AT with the original 240 tach and the 79 electronic distributor and it works.