You need to CHECK it. Get your meter and get to work. Does this sound harsh? NO. It means it is what you have to do. Forget diodes
Clip the meter to the battery. Note the reading. Turn key to "run" Note the reading. Ground the coil wire so it will not fire. Twist to start and crank, and note the reading
Now clip the meter to the coil + wire. Take the same readings, key in "run" note reading and key in "start" and cranking note the reading.
There should not be more than say, .3V between the battery readings and the coil wire readings.
The battery should be 12.6 fully charged. The battery should not sag below 10.5 minimum when cranking.
