No crank, no start 2006 international 4300

Here are some quick pictures of my 2007 4300.
Not sure if they are helpful or not but if you need specific areas let me know and I will see what I can do.

 

Sounds like you cannot see the forest for the trees. They are cleared one tree at a time. You have to test these one wire and or circuit at a time. Other wise you are lost in the woods. Have you followed any of the advise you have been given and what are the results?

 

You don't have a short in the harness, you have an issue with the starter itself and the wiring itself.

The 100 amp mega fuse is there for the body and everything else but the starter. YOU should have another line going to the starter from the batteries, nothing in between. The starter line needs to be on the battery side of the fuse, not the other side.

The starter needs to be replaces, it has a crack in the rear housing and can leak water in very easily. I haven't seen one crack like that in a long time and that one was beaten by some clown with a hammer out of frustration.

 

Double check the cables at the mega fuse. The inner stud, (one closest to the fire wall) should only have cables on it that feed the cab. Outer stud will have power feed from the starter though fuseable links, feed the body controller(also with fuseable links) and feeds for the power distribution box that is right there.

 

I believe the original wire that was disconnected from the starter is where the problem lies.
Some one disconnected it probably because it has an intermittent dead short somewhere in the circuit.
They hooked up that wire when they replaced the starter and maybe the short wasn’t there at that moment but now it has returned.
You could start by disconnecting the wire that they put back on and see what you get then.
That disconnected wire was probably for some high amp draw accessories on the truck that is probably not used now.
Not sure what this truck is used for but does it have anything like a power lift gate or anything like that on it?

 

LPM? Linear power module?