This gate valve operates on the principle of a spring loaded gate balanced against a bimetal element. The tension of the bi-metallic element varies the position of the gate as its temperature changes. The bi-metal element is heated by an electrical heater coil and by the temperature of the ambient air surrounding it. The air valve assembly is installed on the surface of the cylinder head to keep the gate valve closed during hot soak periods.
Heater current for the air valve is supplied by the circuit opening relay power contact, the same circuit which feeds the fuel pump.
Air valve operation can be quick checked by pinching off a supply hose and observing the rpm drop. When checked with a warm engine, the drop should be less than 50 rpm. When the engine is cold, the rpm drop should be high.
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