Thanks for the wiring diagram and the help guys - had the main ground from battery to starter housing in the wrong spot, such a stupid mistake. It was essentially shorting out when starting so that's why starter had so little juice.

That being said, and having driven the truck every day for a good week now, I have noticed some other peculiar behavior. The odometer does not light up until the truck has been running for a few minutes (the mileage screen is just blank for a little while). I also came back to the truck one day and the radio was playing even though ignition was off. I double checked it. Also I turned on the cab fan once and nothing happened, then about 30 seconds later it kicked on. Then I tried to start the truck later on and theft light was blinking and it wouldn't fire. I removed the battery cable for 10 minutes, hooked it back up and all seemed well. All these things happened the first day I drove the truck, and it was raining really heavily out all day. Since then the only consistent issue seems to be the odometer reading. Any ideas? I'm wondering if I might have fried my ECU or something - I can't think of what else would be affecting all different systems like that.

 

The PCM has no direct control to your dash issues, PATS and radio.
There likely is a dash circuit contact issue or remotely the GEM may be involved.
When the PAT don't work the motor will not start.
If you were to do a dash diagnostics it may provide some failure codes to offer some direction to look in.
Good luck.

 

What's a GEM? Googled it but didn't see anything.

What is the system that controls the auto light timer? It also keeps power to the doors and dash lights so I figured it could be something related to that. Thought maybe ECU, or is it just some ignition timer? Either way I think I'm done troubleshooting for now, the thing's just an old POS hunting truck/5th vehicle anyways.

Thanks

 

The General Electronics Module controls a lot of features depending on the vehicle equipage.
Power windows, wipers, 4wd, light timing etc.
It is located on the back side of the fuse panel in the cab.
Check for a leaking windshield or firewall seal dropping water on it.
Good luck.