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'71 240z, MSD 6A Install, Tach Issues


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So after reading for a couple hours now (including some threads just like this one), I'm exasperated. I can't get my stock '71 Tach to work with the MSD setup.

Setup: '71 240z. 280ZX Electronic Distributor w/ E80-12 Module. MSD 6A (Digital). Blaster 2 Coil.

I found this thread that talked about the 8920 Install:


That didn't seem to work. The tach would jump when the engine turned over, but then nothing.

Then I found this one, which exuded so much confidence I figured, 'that must be it' and purchased the 8910.

Getting your early 240Z tachometer working with an MSD 6 Series ignition. - Ignition and Electrical - HybridZ

My tach now works, but only reads about 100-200 RPMs. Someone else there mentions a similar problem, but posts no resolution (I've reached out, nothing yet).

Any advice would be much appreciated.


- The rest of my install works fine, and (apologies for the crude drawing) is as follows:


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Tried this, no luck. In fact, the car wouldn't start when I did that (un-doing it remedied that quickly).

Does anything in that diagram (besides my poor ability to diagram) stand out as incorrect?

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I haven't used an MSD module but I see one thing that might be part of your problem, or just a separate consideration. You are using the ZX ignition module (B and C in your diagrams) to trigger the MSD 6A module. You have two ignition modules. You might bypass the ZX module and use the red and green wires from the VR inside the distributor to trigger the MSD 6A. The ZX module, E12-80, is just one more thing to break down and offers nothing to the MSD 6A system. With the E12-80 module out of the picture you would wire it just like a 280Z electronic distributor (magnetic pickup instructions).

You might still have a tach problem but your system will be more dependable with the E12-80 out.

If I read things right, you would use the violet and green wires to the magnetic pickup in the distributor, and the gray wire to your tach adapter. 6201 instructions.


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