msd question

if your car starts it has to be working because its wired inline ith the factory ignition.

MSD has it on their site. IIRC you use a test light on the output wire from the box (goin to the neg side of the coil) to see if it is pulsing. If it is, the box should be working to some degree. If that works (and you have 12 volts into the coil) but you dont have spark, the coil is a place to look.

Please do check MSD's site to see if I even half-way remember the procedure correctly.
Good luck.