1968 B Body Non Rally Tach Issues

[1mightymopar]

Hey guys, hoping you can bring some sanity to me....!
Hooked up an aftermarket tach and now the car won't start.
I have an MSD coil, just the coil not the whole set up. One wire to the negative on the coil and one to an ignition source. I think it fried 2 orange boxes as well.
If I remove the wire from the coil, the car starts. Put it back on and nothing. Just turns over.
For whatever reason I'm losing spark.

Do I have a bad ground on the tach? Any help is very much appreciated!!

 

[moparnation74]

How did you hook up the tach under the dash? Did you use the factory harnesses separate from the dash harness?

 

[1mightymopar]

How did you hook up the tach under the dash? Did you use the factory harnesses separate from the dash harness?

Yes, it was a non rallye car originally. I ran a seperate wire from the tach to the fuse box and the coil.

 

[moparnation74]

Yes, it was a non rallye car originally. I ran a seperate wire from the tach to the fuse box and the coil.

I would start there......The dash harness is the same for all cars but the tach harness is an additional harness you can purchase....

Just make sure you have the tach wire to the fuse block on the right one.....ck the service manual

In the pic it is the blue wire......

 

[1mightymopar]

That's exactly how I have it hooked up. Could the gauge be grounding somewhere and throwing off the coil?

 

[Shorthorse]

If you're convinced you have everything wired correctly, sounds like you may have a defective tach. What tach do you have? Are you able to put a meter on the trigger wire? Try this, remove the power lead but leave the ground and trigger wire attached?

 

[1mightymopar]

There are only 2 wires coming out of the tach. Power and the negative wire going to the coil. Am I missing a wire or is the trigger/ground the same?
I got the tach from Herb's at Carlisle earlier.

 

[1mightymopar]

This is what my fuse panel looks like. The grey wire is for the tach along with an aftermarket radio.

 

[Shorthorse]

Do you have pictures of the tach, especially the back?

 

[1mightymopar]

Here are pics from the front and back. The needle is up because the speaker magnet is close. I have to shield that somehow.
Could the MSD Blaster 2 coil have something to do with it?

 

[Billccm]

You may want to see if the phonelic washers on the studs are cracked and shorting.
I used rubber grommets to insulate the studs.

 

[Billccm]

https://1drv.ms/v/s!AksXImgz5jdyikKeYPyjTDKAmvNn

 

[1mightymopar]

Thank you very much for your help guys. I'll take a closer look!

 

[lyndondb]

Thank you very much for your help guys. I'll take a closer look!

You can use aluminum foil around your speaker magnet to prevent the distortion on the tach.