96 MCM 3.0LX Won't Start, Tried everything except ______ !? (Starts off Remote Switch)

I usually don't get perplexed but.. New Starter, New slave solenoid, Tried a new key switch which didn't change anything, voltage and grounds all good on everything I have checked, battery, block ground etc. Voltage at key, with key-on at solenoid, at starter, at starter solenoid..Neutral safety is good. There is just a click when engaging momentary of the key-switch. Am I missing a fuse or breaker somewhere that would interrupt the circuit? I figured I wouldn't even be getting the 'click'. The 50 amp breaker looks a little crusty, I'm about to try that next..Or at least jumping it. The engine fired up with remote switch on the starter and ran fine. Only work on a handful of these and each one more a pain than the last.. Any help appreciated. I am almost certain I'm overlooking something electrical between key and solenoid/starter. Any help appreciated!! Serial starts with 0K0 if any relevance.

if you can start engine with jumping starter solenoid only, go backwards, Go to Slave solenoid and use remote switch from SMALL yellow with red stripe to Battery +.

If that works then go try the same except use the Large terminal on the slave solenoid (red wire) instead of the Battery + and see if it starts.

If it starts then you have confirmed the starter and slave solenoids are working correctly.

If it starts with both tests above then now go to key switch and use remote start and a small jumper wire, jump (Red) Battery connection on key switch to Purple wire, use remote and connect to Red to yellow with red stripe. Does it crank and start? If it starts, you MUST pull small jumper to shut it off!!!

If not then you have a bad/weak connection in wire harness or at large black connector where engine harness connects to engine harness

Try all these tests and report back on what works and what doesnt

the relay clicking means your good from the key switch to the slave. Jump the 2 large lugs on the slave , starter works Yes =bad solenoid , No= No power on the Red/Purple wire.or broken wire from slave to starters solenoid. Jump from battery+ to the large Yellow/red , starter works Yes, No

Thank you, will try that in a bit, heading down there in about an hour I'll let you know how it goes. Just to clarify, if the 50amp breaker had some kind of internal malfunction I would not get any click as it would cut all power am I right?

I found the issue... After chasing my tail a bit and doing all the tests mentioned here, I started unravelling the wiring harness after a I had continuity across multiple pins in the harness. Looks like a bunch of old hack repairs gone bad. Thank you all for the info