Electricly challenged...Help!

Took a look at the diagram. That 2B "main feed from starter" where is it connected? I would start right there........damaged wire internally from heat or vibration, or loose nut right there at the starter, if that is where it connects

https://www.americanautowire.com/media/productattachments/files/downloads/92968419 510004 IN 5.0.pdf