The 8.3 cummins usually has a large solenoid mounted on the rear end of the Injection Pump. The solenoid shaft is vertical, Pulls up for run, connected to an arm on the IP. Up is run, down rotates a shaft into the governor housing and blocks fuel flow for shutdown. I have a ford LN8000 dumptruck with the 8.3 and intermittent wiring issue somewhere with that solenoid. It's a dual coil solenoid, Pull up coil is much higher current, hold coil is smaller and pulls less juice. in mine the pull up portion refuses most days. I turn on power, reach under the fender and crank the solenoid into the run position until hold coil grabs and good to go.
I personally still prefer the cable and red handle on the 5.9 in my TC2000 "Tool Bus" No wiring hassles and I can shutdown whenver I want. To a certain degree is offers theft protection, most kids would have no clue what it's for or why it just cranks!!!
If the solenoid or wiring is bad and you just need it running, pull the solenoid up, wrap a piece of bailing wire around it and go crank it. Just have to pull the wire off at the end of the day for shutdown.