In the "good ole days" that pointed to a ballast resistor failure. When you cranked the starter, you got full 12v power to the ignition. When you released the key to the run position, the juice had to flow through the ballast resistor, which cut it down to about 9v to put less wear and tear on the ignition system. It seems that someone told me that at least some of the bricks had the same sort of thing. Check a schematic to see if you've got one.

It could also be an ignition switch problem.