you need to have a full 12 volts to the ignition system. The coil can and does operate on lowered voltage, only after the engine is running. Wont start on that lowered voltage, thus why they are wired the way they are ( ign' 1 and ign' 2 ).
We have very large wires going directly to the starter so it can draw the lions share of whatever voltage is there.
The rest of the vehicle operates vis separate much smaller wires with a crowd of connections offering additional voltage drop. The disconnect at fusible link and bulkhead terminals are the most common places to find weak connections.
