Dual fuel common rail depressurization during engine shutdown and machine using same

A machine comprising:

• a machine body;
• an engine supported on the machine body and including an engine housing that defines a plurality of cylinders;
• a piston positioned to reciprocate in each cylinder of the plurality cylinders to define a compression ratio greater than 14:1;
• a plurality of fuel injectors, each fuel injector of the plurality of fuel injectors including a gaseous nozzle outlet set and a liquid nozzle outlet set positioned for direct injection into a corresponding cylinder of the plurality of cylinders;
• a gaseous fuel common rail and a liquid fuel common rail fluidly connected to a first fuel inlet and a second fuel inlet, respectively, of each fuel injector;
• and
• an electronic controller operatively coupled to each fuel injector, the electronic controller being configured to
• receive a signal indicative of a gaseous fuel pressure within the gaseous fuel common rail,
• receive an engine shutdown command signal, and close a gaseous fuel shutdown valve in response to the engine shutdown command signal, the gaseous fuel shutdown valve being disposed upstream of the plurality of fuel injectors, and
• continue running the engine after the engine shutdown command signal according to an engine shutdown algorithm, the engine shutdown algorithm including
• maintaining a liquid fuel pressure in the liquid fuel common rail greater than the gaseous fuel pressure in the gaseous fuel common rail,
• injecting gaseous fuel into the plurality of cylinders at a normal gas injection timing responsive to the gaseous fuel pressure being greater than a first threshold pressure, the first threshold pressure being greater than a top dead center (TDC) cylinder pressure,
• injecting gaseous fuel into the plurality of cylinders at an advanced injection timing responsive to the gaseous fuel pressure being less than the first threshold pressure and greater than a second threshold pressure, the advanced injection timing being earlier than the normal gas injection timing and earlier than a top dead center timing of a corresponding piston on a compression stroke, the second threshold pressure being less than the TDC cylinder pressure and greater than a shutdown threshold pressure,
• operating the engine according to a cylinder cut out mode responsive to the gaseous fuel pressure being less than the second threshold pressure and greater than the shutdown threshold pressure, such that inactive cylinders of the plurality of cylinders do not receive gaseous fuel during a cycle of the engine, and active cylinders of the plurality of cylinders receive gaseous fuel during the cycle of the engine,
• stopping the engine when the gaseous fuel pressure is less than the shutdown threshold pressure, and
• reducing the liquid fuel pressure in the liquid fuel common rail to less than the threshold shutdown pressure after the gaseous fuel pressure is reduced below the threshold shutdown pressure.