Tried to start the car this morning and it just cranked forever no start. Checked the plugs fine. Broke out the spark tester no spark. So I undo the ignition box from the harness and run the original harness to the original ignition and the car starts. How do I test if the box is bad?

 

Looks like you already peformed a check on the box. I would check all the grounds to it and try it again.

 

If the box has power and ground going to it and doesn't work, send it back to MSD for repair.

 

How much do theycharge?

 

One time we sent one and it was free, the other it cost $50. I guess it depends on the circumstance.