Here’s a partial answer, but the diesel tech / 24v forum is where the answers are.
“The issue is that the factory starter relay (that activates the starter solenoid) is controlled by both the ignition switch and the voltage converter timer. Power comes in to the relay coil from ignition switch (crank position) and is grounded through the voltage converter timer. Once the voltage converter relay is removed the voltage converter timer will no longer ground the starter relay coil and the starter solenoid with not get power when the key is in the crank position.”