The fuel tank pressure sensor is located on top of the fuel tank assembly.
There should be an access plate located in the rear of the vehicle under the carpeting. Remove and you should be able to see the top of fuel tank assembly. The sensor has a hose and an electrical connector and a nut that you remove to pull out the sensor.
Hope this helps.
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December, 7, 2008 AT 8:24 PM
Here is the info you requested.
Also, looks like you may have some recalls on your vehicle. The dealer may fix these for free. Please contact the dealer service department, give them the VIN number of your car and have them check on these to see if they apply to you.
Raise the vehicle.
Remove the fuel tank. Refer to Fuel Tank .
Remove the fuel tank vapor pressure sensor electrical connector.
Remove the fuel tank pressure sensor.
Install the fuel tank vapor pressure sensor.
Install the fuel tank vapor pressure sensor electrical connector.
Install the fuel tank. Refer to Fuel Tank .
Lower the vehicle.
The Fuel Tank Pressure sensor is a 3 wire strain gauge sensor much like that of the common Manifold Absolute Pressure (MAP) sensor. However, this sensor has very different electrical characteristics 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 sends a voltage between 0.1 and 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 to 1.7 volts.
When the air pressure in the tank is 4.5 inches H2O (1.25 kPa), the sensor output voltage should measure 0.5 + 0.2 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 at 14 inches of H2O (-3.75 kPa).
December, 12, 2008 AT 8:51 PM
On the 98 you can change the pressure sensor without dropping the tank. It's a tight fit but doable. Jack up the rear of the blazer. Look at the end of the tank and you will see the fuel lines and connections to the left side. The pressure sensor plugs in to the top of the pump module to the right side. Use a brush and compressed air to clean the dirt and crap away before you pull it. Once you have cleaned the stuff away you can use a screwdriver to pry the sensor out of the hole. Then once you have it out you can unplug the connector and plug it into the new sensor. Put a dab of silicone grease onto the rubber boot and then push it into the hole.
Takes about 20 minutes to do and you don't have to drop the tank. The sensor will JUST clear the pump and body.
No access panel on the Blazers. Only a few GM models have access holes for the pumps.