Honda EXT12D Maintenance Manual page 22

According to season and ambient temperature, a different grade of
diesel fuel should be used. The fuel might freeze and prevent the
engine from starting if summer fuel is used in winter. If winter fuel is
used in summer, it could result in a lack of power. Be sure to use the
proper grade of diesel fuel which complies with the ambient
temperature.
Refill the fuel frequently, especially in winter. Water could
accumulate if there is much air in the fuel tank. We recommend that
you refill after each use of the generator.
Air bleeding (Restart of the engine after the fuel has run out)
The generator is equipped with an automatic air bleeding system.
Set the automatic throttle switch to ON position, make sure that fuel is
supplied to the fuel filter, and start the engine without load.
Light blue exhaust gas is seen while bleeding air. Keep the engine
running, and the exhaust smoke color leans and the engine speed
stabilizes after the air bleeding.
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