To make it clearer, Amel uses a “floating”, or “isolated” ground system that disconnects battery negative from the bonding (zincs) system. It makes a connection to the engine block only when the starter, stop solenoid, or glow plugs are energized. A solenoid in the line between battery negative and the engine block is energized to complete the circuit. There are three diodes in the circuit that prevent a feedback loop which would energize the stop and start solenoids at the same time. If the stop diode failed, the button wouldn’t work. If the start diode shorted, you would hear the starter motor when you pushed the stop button.
If the stop diode shorted the engine wouldn’t start because the stop solenoid would be energized when you keyed the engine to start.
Craig, Bill, Danny, etc, if I don’t have this quite right, please correct me, .