The fuel sending unit on the Chevy Trailblazer is a component that uses a float to measure the amount of gas in the gas tank. It acts as a potentiometer and sends readings back to the gas gauge. Signs that the fuel sending unit may be going bad include inaccurate gas gauge readings or the vehicle sputtering like it may be running out of gas. The fuel sending unit on the Trailblazer is part of the fuel pump, so if the unit goes out, the fuel pump should be changed, too.
Remove the spare tire if it mounted on the rear underside of the Trailblazer.
Pop the Trailblazer hood and remove the negative battery cable with a socket set. Also open the fuse box and remove the fuse to the fuel pump. The fuse location is marked on the fuse diagram on the inside lid.
Open the gas tank and gas cap, slide the siphon tube in and use the hand pump to transfer the gas from the gas tank into several gas cans.
Jack up the vehicle and lower the rear end down on jack stands. Make sure that the emergency brake is also engaged.
Roll the jack directly underneath the center of the gas tank and jack it up so that it rests against it.
Remove the bolts holding the gas tank's metal straps in place with the socket set. Gently lower the gas tank so that the top of the tank can be accessed.
Remove the gas hose clamp with a screwdriver and then unfasten the plastic wiring connections to the tank.
Lower the tank completely and slide it out. Pry the retaining ring from the top of the tank and then pull the old fuel pump out. Place the new fuel pump assembly in with a fresh O-ring and then slide the tank back underneath the Trailblazer. Jack the tank back up about halfway.
Reconnect the electrical wiring and the fuel hose and then jack the tank fully back into position. Set the gas tank straps into place and secure them with their bolts.
Jack up the vehicle and remove the jack stands. Also place the spare back underneath the Trailblazer.
Reconnect the negative battery cable and the fuel pump fuse.
Place the gasoline back into the Trailblazer's gas tank.
