Starter clicks using the key, engine starts by jumpering the relay
When you are jumpering the starter relay are you providing 12v to the yellow IGN 2 on the relay?
Below is based on 67 dart automatic.
74 might be wired differently
If you are going from bat to sol (black line) you are bypassing the starter relay.
If you are providing 12v to the IGN 2 post blue line you are bypassing the ignition switch
The black line only proves the starter is good.
The blue line will prove the starter relay and the starter are good. (Assuming the NSS wiring is intact and functioning correctly. )
The key / NSS seems to function as you hear a click. But if the voltage at the starter relay (yellow) is low due to high resistance at the many junctions the relay might not be pulling in fully.
My gut says the starter relay is your first place to check
When you are jumpering the starter relay are you providing 12v to the yellow IGN 2 on the relay?
Below is based on 67 dart automatic.
74 might be wired differently
If you are going from bat to sol (black line) you are bypassing the starter relay.
If you are providing 12v to the IGN 2 post blue line you are bypassing the ignition switch
The black line only proves the starter is good.
The blue line will prove the starter relay and the starter are good. (Assuming the NSS wiring is intact and functioning correctly. )
The key / NSS seems to function as you hear a click. But if the voltage at the starter relay (yellow) is low due to high resistance at the many junctions the relay might not be pulling in fully.
My gut says the starter relay is your first place to check
