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Discussion Starter · #1 ·
Hey guys,

So this is the second time I've attempted this. Once bypassed, the car seems to run the same (at idle at least) as if the msd is hooked up.

My problem is my aftermarket Autometer tach is erratic while idling. It's bouncing from 1,000-2000 rpms even though the engine isn't.

I took the tach trigger wire from the MSD and attached it to the negative side of the ignition coil.

What I can't understand is why I have another wire spliced into the positive side of the ignition coil. Per all the instructions I've found on installing a MSD ignition, no wire should need to go to it.

Both of these wires that I mentioned I believe go inside the car. I have a Florida 5.0 Autometer gauge setup.

My MSD is mounted right where the battery normally is. I planned on putting the battery back in the engine bay. So I thought about going back to the stock ignition setup. If I can't figure this out, I may just try to mount the MSD ignition box inside the fender.

Sorry for the long post.



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Discussion Starter · #3 ·

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Discussion Starter · #5 ·
sounds like you have TWO supplies to the coil positive

remove one
Basically with MSD hooked up and everything working, I have a wire going to the positive side of the coil. The tach output wire from the MSD goes into the firewall. Same with that wire from the coil.

Best would be to track down where they go. But I'll probably just leave it alone for now.

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Discussion Starter · #8 ·
The coil is fired more than once at idle and low rpm this is called MSD. Not to be confused with the brand.

MSD is multi spark discharge. The coil is refired after the initial fire to aid in emissions.

You might be better off stealing a signal from the injector and not the coil.
Good information thank you. I just reinstalled it like it was before. My car has the wire tuck, so they are all in the fender.

I ordered a LMR battery kit. I plan on keeping the ignition box, so I'll have to mount it elsewhere.

I was pretty close to installing my new Crane fireball ignition box. But I'll save it for when it's needed.

I did install a screaming demon coil.

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Discussion Starter · #10 ·
Tach output should only be wired to your aftermarket tach input and not to the coil. With the stock tach, nothing extra is needed. View attachment 1060218
Yup, I'm not sure what wire is going to the coil. I'd have to pull instrument cluster to find out. Everything works this way.

It's when I tried bypassing MSD ignition that I had problems. I then put the wire that was connected to the MSD tach output (from tach gauge) to the negative side of the coil. Rpms were erratic.

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