FLD Electrical Problem

You do not have adquate voltage to boot your ECM and keep it booted prior to cranking your engine.

Take a look and load test those batteries to be sure they are still good. I just thew away a expensive deep cycle battery for almost three years old and failing to hold adequate charge on it's fancy construction. Someting to do with the spiral gel technology I think it was.

Anyone old enough tor remember those wonderful old lead acid batterries?

 

There should be a starter solenoid on the fire wall on the driver side. take a pair of pliers and jump the 2 large terminals. it should turn over. If it turns over then you know it's not the battery's or cables going to the starter. from there I would start checking wires going into the cab, including ECM wire from the battery's, key switch, starter button, relay's.