Fuel Tank Pressure Sensor: Description and Operation

Fuel Tank Pressor Sensor:

The fuel tank pressure sensor is a 3 wire strain gauge sensor much like that of the Manifold Absolute Pressure (MAP) sensor, however this sensor has a very different electrical characteristic due to its pressure differential design. The sensor measures the difference between the air pressure, or vacuum, in the fuel tank and the outside air pressure.

The sensor mounts at the top of the fuel tank sending unit. A three wire electrical harness connects it to the control module. The control module supplies a 5 volt reference voltage and ground to the sensor. The sensor varies a voltage between 0.1-4.9 volts. When the air pressure in the fuel tank is equal to the outside air pressure, such as when the fuel fill cap is removed, the output voltage of the sensor will measure 1.3-1.7 volts.

When the air pressure in the tank is 4.5 inches Hg (1.25 kpa), the sensor output voltage should measure 0.3-1.7 volts.

The sensor voltage will be approximately 1.5 volts when the fuel tank pressure is equalized with ambient pressure. The sensor voltage increases to approximately 4.5 volts when a vacuum of 14 inches of Hg (-3.75 kPa) is detected.