I just finished installing an in dash tach in place of the fuel gauge.

The tach seems to work only when the starter is cranking. Once the engine stars, the tach stops working.

I have the ignition wire hooked up to the negative coil terminal and the 12V wire to a switched 12V source. I also tried a constant 12V source.

I have an MSD ignition box on the car. Does the tach need to be wired differently with the MSD?

Any help would be appreciated.

 

First lets check your wiring, green to (-) negative on coil or you could have a tab or your MSD box, Red to 12v power source, Black to ground, White to your lighting circuit.

If this is correct, some tachs require you to use a tach adapter with MSD boxes.

If you got you instructions still from your MSD box, there is a section that talks about this. If you don't have them, go to MSD and download the instructions for you box and checkto see if you need an adapter.

I can tell you, if it's Autometer, you shouldn't need an adapter with MSD boxes.

 

Thanks for your reply. I went to the MSD site and found that there is a tach hook up on the side of the box.

I used that hook up and the tach works fine now.

 

Glad I could help....have fun