On the older systems there is a separate power path for ignition system when key is in START and when it is in RUN
This was to help with Cold Starts and prevent coils from over heating.
When engine is running coil only needs 8volts for spark, any more than that just makes more heat and coil has a shorter life, so a resistor is added to the RUN power wire going to the coil "+".
But when starting, the starter motor draws battery voltage down to 9volts, the resistor power would drop to below 5volts and spark would be very very weak.
So a second power wire was needed for starting, this was often run from the Starter Relay on the fender, the "i" post on a 4 post relay, to the coil "+".
But they also used the Clutch switch(manual trans) or the NSS(automatic) to pass the direct power to coil for starting.
You can trace this wire or add you own new wire.
To add a wire you need a diode and 18gauge wire.
The diode is needed to prevent RUN power from flowing backwards thru the new wire.
A diode has a direction arrow on it, power will flow in the direction the arrow points.
You get this power from the starter relay.
Either from the "S" post, only has 12volts when key is in START
Or from the Starter Motors larger cable hook up, also only has power when key is in START.
So install the new wire on either with diode pointing towards coil "+"
Starter relay------diode>>------coil "+"
Leave existing wire on coil "+", it is still needed for RUN power