Fuel Temperature Sensor: Description and Operation

The fuel temperature sensor is located in the fuel return line directly down stream of the fuel rail pressure control valve. The sensor measures the temperature of the fuel in the return pipe between the rail and the pre-heating valve. The sensor ranges from -40° F (- 40° C) to 284 °F (140° C). If the engine is cold, the actual value sent will read ambient temperature. The value rises after the engine has been started.

An negative temperature coefficient (NTC) resistor integrated in the fuel temperature sensor alters it's electrical resistance in line with the fuel temperature (the resistance drops as the temperature rises). If fuel temperature has reached 248° F and engine speed is above 2000 rpm, a pumping element of the high pressure fuel injection pump is switched off and engine output is reduced.