My 70 Duster Big Block Car

Wants to fire while the key is in crank position but quits when the keys is turned back to the run position? Thats the ballast resistor. You can confirm this by bypassing it. Run a wire from the pos batt terminal to the coil side of the ballast. Then crank it. If it fires and runs you have your culprit. Cant shut the motor off with the key if you do this though and dont run it more than 1/2 hour because the ign system is recieving full battery voltage. Just dissconnect the jumper wire to kill it.

I made a jumper wire from some 14 gage and 2 alligator clips.