My '67 Ford Falcon had this EXACT problem. what happened is it would get the 12v to the coil on cranking, fire up then die from no voltage. I ran a jumper wire from the solonoid I terminal ( for cranking bypass ) to the + side of the coil. this corrected the problem. I never fixed the problem wire, tore the engine apart b4 I got to it. and it will be fired with a DS2 distributor, and MSD 6 BTM, so I'll be replacing it anyway. I don't know why it got 7 volts to the starter solonoid, but that's what my DVOM read. was 0 at the coil.