68 Roadrunner no spark while cranking fires when releasing key to run.

[The Beep]

This has me stumped, and I'm supposed to be an electronics tech! The car has an MSD Street fire ignition, 4 speed and a 383. There is no ballast in the ignition setup. The problem has existed for years prior to the MSD conversion.

While cranking with the ignition key switch there is no spark, however when the key is released to the run position voltage is applied and the car fires and runs fine. The car shuts down fine with the key and all accessories operate correctly.

If the key is set to the run position and you jump the starter solenoid it also fires right up (I actually have a push button under the dash to do this... ).

I have tried 2 other ignition switches and just yesterday replaced the engine harness with a new Year One item. The under dash harness is original but appears decent. I do have a new one but not sure I would survive 2 hours upside down trying to replace it!

Any ideas?

 

[The Beep]

Success!

For an electronics tech I sure feel like an idiot. Put up with this for 15 years. Actually looked at the wiring diagram for 15 minutes and there it was. Gotta jumper the wires for the unused ballast resistor. Now power while cranking with key AND power on the run position.

Vroom!!!!

 

[Basket case]

got love electrical troubles...