One day the stang ran fine. Then all of the sudden it will crank but not fire! I checked the coil, it was good. Thought the dizzy was bad, Hooked up an MSD box and changed to a duraspark distributor...... still won't run. I tested the MSD box, it has spark at the coil. I checked for voltage at the silinoid on the little posts..... No voltage there with the key on. What does this mean? I also checked for voltage on the little post wires. NONE. What is wrong here?