The bulkhead connector in question is wire J3 connector pin D. J3 is a #14 AWG brown wire and should be the top left corner (top row of connectors all the way to the left).

You can stick a voltage probe in that connector while cranking and see if you have full battery voltage. You can also remove the plastic connector and inspect the connections.

Or you can do what I suggested up and jumper that wire for testing............