Has good batteries, everything good, no juice, not getting power to the cyllenoid, checked all relays appear to be good. Does this truck have fuses? Or does the start button just go out?
Look for the extra starter sol. hanging on firewall under air valves, CK. by using small wire to cross small sol. wire with hot wire on starter, follow wires from starter if all fails?
Start buttons do go out, but I would also check the clutch switch. Some will not start if the computer does not see that the clutch is pushed in.
Follow the wires coming out of it and check the restistance on it. It should show OL or open with the pedal out and a resistance with it pushed in when the switch is closed.
Sometimes if the clutch pedal is really out of adjustment it will not engage the sensor and will not start.