Help Firing Dad's Dart up Again - SOS - No Spark After Hosing Off the Dust

So, I'm not fully understanding this interlock that his car has. Apparently it is still installed and was giving them problems early on and preventing the car from cranking. Currently it is still hooked up and the car will crank but they're not getting spark. They can jump the 2 yellow wires together and still get crank with no spark. There is a blue wire that is hot that they can jump and the car still cranks. They can't find any "blue box" that is referenced in some other posts I've read about the interlock.

Anyone have a link to the definitive guide to this interlock? Can it only prevent cranking, and if the car is cranking it's okay? Is it possible there is an interlock issue that would cause it to crank buy not have spark? They're slowly going through each leg of the ignition wiring looking for a short and they haven't found anything yet. They're grabbing a bite to eat and then will dig into post above from @67Dart273. They're going to power on and attempt to get the car running again before Thursday. They'll have a few hours tonight, a few in the morning, and then try again on Wednesday afternoon after they've celebrated Christmas with their families.

Of course we'd go from lighting on the first crank to this just by trying to hose off the dirt :(.