A detailed view of the diesel engine (background) and pony motor (foreground).  The pony motor is a two-cylinder gasoline engine, with typical spark plugs and a carburetor.  It is hand-started using a removable crank.  The pony motor shares coolant with the diesel and, when running, helps warm the diesel's engine block.  The exhaust from the pony motor flows through a heat exchanger surrounding the intake manifold of the diesel, preheating the air for the diesel to ease starting.

The aft end of the unit showing the compressor assembly, aftercooler, and air receivers.