74 Dart won't start - ignition switch - maybe starter relay?

^^But you can screw yourself, here, and I've posted this before^^

If you troubleshoot a no-start condition, and DO NOT USE THE KEY to operate the starter, you CHANGE the voltage condition at the coil

1....Normal operation,

A: Key in run, engine stopped. You will NOT see 12V at the coil, you will see much lower, because of the ballast, perhaps 6-10V

B: With key twisted to start and monitoring coil V, it should be "same as battery" while cranking, and it will be whatever the battery is at that point, say, 11V. So crank it, read the coil, move meter to battery, crank again and read battery. You need AT LEAST 10-10.5V while cranking. If not STOP and fix the problem, might be as simple as dead battery

2....Abnormal

A: Again, key in run engine stopped, coil voltage same as (1) above, about 6-10V

B: Cranking engine while jumpering starter relay, YOU NOW are operating with the key in "run" and the battery pulled down further due to cranking load, so the coil will now ONLY GET maybe 4-6V while doing so. This FURTHER reduces spark output if you had any to start with.

ALSO BEAR IN MIND that during cranking, and because of the loss of IGN1 "run" and the transfer to IGN2, that THE FACTORY ELECTRONIC MODULE gets MUCH less voltage because it is fed BACKWARDS through the ballast resistor.