Fuel Control Valve. The Fuel Control Valve (6/18) is mounted on the Fuel Injection Pump. It is normally de-energized. In the de-energized position, the high pressure output from the Injection Pump is bypassed into the fuel return line. The injector does not receive fuel.

Off/Run/Start Switch.
+12 volts is taken from the starter post, through the wiring harness (red wire), and applied to the terminals of the Off/Run/Start switch located on the control panel.
 
Run Position. When the Off/Run/Start switch is moved to the Run position, +12 volts is applied back through the harness (green wire) to one side of the water temperature switch. This switch is normally closed, so the +12 volts will pass through the switch to the exhaust temperature switch, and also through the harness (brown wire) to the water lamp. The water lamp will illuminate because the engine coolant temperature is below 185 degrees F.
 
Since the exhaust temperature switch is also closed, the +12 volts goes to the oil