Voltage problems, cutting out when hot
If you are looking in the '74 FSM, it probably has a wiring diagram like the '73. This is snip from the '73 so details may not be exactly the same.
Here's how you decipher it.
J is the Ignition circuits.
J2A is ignition power feed when key is in run position. 16 DBL is 16 gage Dark Blue. The original ECU got power in run through J4 through a 5 ohm resistor.
A more recent ECU will get all power simply through J2E.
If we follow J2C back, not shown in the snippet above is an oval marked CE2 N
The ovals marked CE are connectors, and the key for them is several pages later. CE2 is the bulkhead connector. N is the cavity. So the blue with white trace is the power feed when the key is in run position.
OK. 67Dart273 has probably given you the most direct way to identifying the power feed.
If you are looking in the '74 FSM, it probably has a wiring diagram like the '73. This is snip from the '73 so details may not be exactly the same.
Here's how you decipher it.
J is the Ignition circuits.
J2A is ignition power feed when key is in run position. 16 DBL is 16 gage Dark Blue. The original ECU got power in run through J4 through a 5 ohm resistor.
A more recent ECU will get all power simply through J2E.
If we follow J2C back, not shown in the snippet above is an oval marked CE2 N
The ovals marked CE are connectors, and the key for them is several pages later. CE2 is the bulkhead connector. N is the cavity. So the blue with white trace is the power feed when the key is in run position.