1991 4.0 no crank issue

[91HOpioneer]

First post to the club, but a frequent user of the great advice you guys offer. 
Having a crank issue with a 91 4.0

Have power, but as soon as I turn the key completely to ignition I hear one click coming from the starter, the starter is trying to engage but then I lose all power and Can not keep trying to crank until I disconnect the battery and the reconnect to have the same thing happen. 

 

Things I’ve checked and or replaced: 

Starter

Starter wires

Grounds

Ignition switch 

nss (completely replaced)

all relays and fuses

battery (used multiple different batteries to be sure)

battery terminals and negative and positive terminal clamps 

radio and speakers (checking for shorts)

Fuel pump ballast resistor  

map sensor 

and probably a few others that I’m forgetting 

Probably have about 25 hours in to this problem and I’m at a complete loss. Maybe I messed something up along the way so feel free to give any knowledge of common mistakes made during install or my checks along the way. 
I hope what I’m trying to say is clear and if not I can clarify 

[jdog]

Have you changed the starter relay?

[Green Mesa XJ]

Is the motor locked up? Can you turn with a hand tool at the bolt for the crank shaft pulley?


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