Replacing Fuel Sending Unit In A 2005 Trailblazer

Replacing the fuel sending unit on a 2005 Trailblazer is a complex task that requires a range of tools and a good understanding of car mechanics. The fuel sending unit is located in the fuel tank and sends a constant signal about the amount of fuel remaining. When it fails, the fuel gauge stops working, and the check engine light may come on.

There are several steps to replacing the fuel sending unit, and they are outlined in detail in several online forums. The first step is to locate and remove the fuel pump relay in the fuse box under the hood, which will cause the engine to die. Next, crank the engine a few times to release pressure in the fuel system, and remove the battery negative. It is then necessary to raise the car with a floor jack and support it with jack stands or a ramp. The next steps involve siphoning fuel from the gas tank and removing the fuel filler pipe, the frame crossbar under the fuel tank, and the fuel tank brace bars.

The next steps involve removing several lines and connectors, including the vent valve line, the electric connector, the filler pipe, and the fuel line connections. With these removed, the fuel tank can be lowered and the fuel pump removed. This requires a fuel pump wrench or a large screwdriver and hammer to hit the fuel pump secure ring.

The new fuel pump can then be installed, and the various lines and connectors reattached. The fuel tank is then raised and the brace bars and frame crossbar reattached. Finally, the vehicle can be lowered, the fuel pump relay reattached, and the battery reconnected.

Disconnect the battery and relieve gas pressure

Disconnecting the battery and relieving gas pressure is an important step when working on the fuel system of your car. Here is a detailed, step-by-step guide on how to do this for a 2005 Trailblazer:

Step 1: Disconnect the battery

Locate the battery in your car. It is usually in the engine bay, but it can also be in the trunk or under a seat. Once you have located it, identify the negative terminal. This will be clearly marked with a minus (-) sign. Using a wrench or a socket, loosen the nut that holds the negative battery cable in place. Do not allow the wrench or socket to touch any other metal parts of the car, as this could cause a short circuit. Once the nut is loose, carefully remove the cable from the battery terminal.

Step 2: Relieve gas pressure

• Locate and remove the fuel pump relay in the fuse box under the hood. The engine will die within a few seconds.
• Crank the engine a couple more times to release pressure in the fuel system.
• Open the fuel filler cap to relieve gas pressure.
• Siphon as much fuel as possible from the gas tank to make it less heavy and easier to remove. You can use a siphon tool from an auto parts store for this.
• If you are unable to insert the siphon pipe into the tank, remove the fuel filler pipe. Loosen the two crimps holding it in place using a 7mm socket, then rotate and remove the plastic fuel pipe from the tank.
• Once the filler pipe is removed, insert the siphon tool directly into the tank and siphon the fuel into a gas can.

By following these steps, you will be able to safely disconnect the battery and relieve gas pressure in your 2005 Trailblazer, making it ready for further repairs or maintenance.

Remove the rear driver's side seat and trim

To remove the rear driver's side seat and trim of a 2005 Trailblazer, follow these steps:

Removing the rear driver's side seat:

• Move the seat forward and remove the two bolts that secure it in place.
• Pull out the seat.

Removing the trim:

• Remove the trim from the bottom of the rear driver's side door jamb and the B-pillar trim.
• Make a couple of inconspicuous cuts in the carpet to move it out of the way. Be careful of the wire loom that runs over the fuel pump.

Now you should have access to the fuel pump and can proceed with the rest of the fuel sending unit replacement procedure.

Cut a hole in the floorboard to access the fuel pump

To cut a hole in the floorboard of your 2005 Trailblazer to access the fuel pump, you will need a couple of air tools: a pneumatic nibbler and a pneumatic hammer.

First, you need to access the floorboard. Remove the rear driver's side seat. There are just two nuts to remove. Move the seat forward, take off the two bolts, and pull out the seat. Then, remove the trim from the bottom of the rear driver's side door jamb and the B-pillar trim. Move the front driver's seat up to give yourself more room.

Next, you need to move the carpet. Make a couple of inconspicuous cuts, being careful of the wire loom that runs over the fuel pump. Drill a 3/4" hole to figure out exactly where the pump is, so you know where to cut. The fuel pump is located between the two studs that hold the seat down. Once you know where it is, use the pneumatic nibbler to cut as big a hole as you can over the fuel pump. You can use a socket to hold the wire loom up and out of the way.

There is a weld forward that will be your northern boundary. The raised area where the seat mounts will be the western, eastern, and southern boundaries. Rotate the head of the nibbler if needed. Once you have a rectangular shape cut out, pull relay 41 and crank the engine to depressurize your fuel system.

Now you can remove the fuel lines from the fuel pump by pinching the clip and pulling the hose off. Rust may get stuck between the clip and the line, so you might need to wiggle them until they break off, making it easier to remove the lines from the fittings.

Before and after removing the ring, vacuum off all the rust and crescent-shaped pieces of metal. Using the pneumatic hammer, knock the retaining ring off.

Now, install your new pump and lock ring. Reconnect the fuel lines and electrical connector. Start your truck to see if gasoline is still leaking.

Paint the edges of the floorboard that you cut to prevent rust, then use the pneumatic nibbler to cut a piece of sheet metal that is slightly bigger than the hole. Paint it, then put a bead of RTV around the hole, and pop in some rivets. Replace the padding and carpet. Reinstall the trim pieces and rear seat.

Disconnect the fuel lines and electrical connector

Disconnecting the fuel lines and electrical connector is a crucial step in replacing the fuel sending unit of a 2005 Trailblazer. Here is a detailed, step-by-step guide to help you through the process:

Step 1: Remove the Fuel Filler Pipe

Locate the fuel filler pipe at the rear of the vehicle. To remove it, first, loosen the two cramps using a 7mm socket. Then, rotate and remove the plastic fuel pipe from the tank. This may be tight, so ensure you loosen the right-side pipe from the metal pipe to allow easy rotation and removal.

Step 2: Siphon the Fuel

Use a siphon tool to remove the fuel from the gas tank. Insert the siphon pipe directly into the tank and siphon the fuel into a separate gas tank. This step is important as it makes the tank lighter and easier to handle during the replacement process.

Step 3: Remove the Fuel Tank Brace Bars

Before removing the fuel tank brace bars, place a piece of plywood board underneath the tank and use a floor jack to support it. Then, use a socket to loosen and remove the screws on the drive-side brace bar. The passenger-side brace bar is not screwed in; instead, it is inserted and rotated 90 degrees to hold it in place. Remove this bar by simply releasing and rotating it out of the frame.

Step 4: Disconnect the Vent Valve Line

Locate the vent valve line, which is a black line with a white connector at the center, and remove it using a quick-connection clip. You will also need to remove the red/blue electric connector attached to the vent valve.

Step 5: Disconnect the Thinner Vent Line

At the rear of the car, near the top of the tank, you will find a thinner vent line with a white connector. Disconnect this line from the tank using a quick-connection clip.

Step 6: Disconnect the Fuel Lines

Go to the front of the fuel tank and locate the two fuel line connections. These lines also use quick-connection clips (part number: 800-023). Carefully disconnect both lines, being mindful of any residual gas.

Step 7: Lower the Fuel Tank

Now, you can slowly lower the fuel tank using a floor jack. Remember to remove the two electrical connectors at the top of the tank before completely lowering it.

Step 8: Remove the Old Fuel Pump

To remove the old fuel pump, you may need to use a specialized fuel pump wrench (J-44402) or a large screwdriver wrapped with tape (to avoid creating sparks) and a hammer to hit the fuel pump's secure ring. Loosen and remove the ring, and then take out the old fuel pump.

Step 9: Install the New Fuel Pump

Installing the new fuel pump is the reverse of the removal process. Ensure you use a new gasket and connect all the lines and electrical connectors securely.

Step 10: Reinstall the Fuel Tank and Brace Bars

Carefully raise the fuel tank and reinstall the two fuel tank brace bars and the frame crossbar. Double-check that all connectors are secure and properly connected.

Step 11: Finalize the Process

Raise the vehicle, remove the jack stands, and lower it back to the ground. Reconnect the fuel pump relay and the battery negative terminal. Turn the car to the "On" position a couple of times to prime the fuel pump before starting the engine.

Remember to work in a well-ventilated area and take the necessary precautions when working with fuel and electricity. It is also recommended to have an assistant to help with the process, especially when raising and lowering the fuel tank.

Remove the old fuel pump and sending unit

To remove the old fuel pump and sending unit from your 2005 Trailblazer, follow these steps:

Step 1: Remove the rear driver's side seat

Move the seat forward, take off the two bolts, and pull out the seat.

Step 2: Remove the trim

Remove the trim from the bottom of the rear driver's side door jamb and the B pillar trim.

Step 3: Move the front driver's seat

Move the front driver's seat up to give yourself more room.

Step 4: Cut the carpet

Move the carpet by making a couple of inconspicuous cuts. Be careful of the wire loom that runs over the fuel pump.

Step 5: Drill a hole

Drill a 3/4" hole to figure out exactly where to cut. The fuel pump is between the two studs that hold the seat down.

Step 6: Cut a hole for access

Use a pneumatic nibbler to cut a rectangle-ish shape over the fuel pump. Use a socket to hold the wire loom out of the way. The weld forward will be your northern boundary, and the raised area where the seat mounts will be the western, eastern, and southern boundaries.

Step 7: Depressurise the fuel system

Pull relay 41 under the hood and crank the engine to depressurise the fuel system.

Step 8: Remove the fuel lines

Remove the fuel lines from the fuel pump by pinching the clip and pulling the hose off. Rust may get stuck between the clip and the line, so wiggle them until the lines break off.

Step 9: Remove the retaining ring

Use a pneumatic hammer to knock the retaining ring off. Vacuum off all the rust and crescent-shaped pieces of metal before and after removing the ring.

Step 10: Remove the old fuel pump

With the ring removed, pull out the old fuel pump.

Step 11: Install the new fuel pump

Put the new fuel pump and lock ring in place. Reconnect the fuel lines and electrical connector.

Step 12: Test the new fuel pump

Start your Trailblazer to ensure gasoline is not spewing out.

Step 13: Paint the edges of the floorboard

Paint the edges of the floorboard that you cut to prevent rust.

Step 14: Cut a sheet of metal

Cut a sheet of metal similar in thickness to a little bigger than the hole. Paint it and put a bead of RTV around the hole before popping in a few rivets.

Step 15: Reinstall the carpet and trim

Replace the padding and carpet. Use sticky tape to stick the carpet together where you cut. Reinstall the trim pieces and the rear seat.

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