•  If the wax component in the fuel becomes greasy and clogging occurs in the fuel filter, a vacuum is generated in the fuel passage between the fuel filter and the injection pump. If the pressure inside the fuel passage decreases to approx. -31.3 kPa {-235 mmHg, -9.23 inHg} or less, the vacuum switch is turned on and power is supplied to the fuel warmer heater. The greasy wax component is heated and melted by the fuel warmer heater. When the pressure inside the fuel passage increases to approx. -18.7 kPa {-140 mmHg, -5.51 inHg} or more, the vacuum switch is turned off and the power to the fuel warmer heater is cut.