Replacing The Fuel Sender In Your Qx56: A Step-By-Step Guide

The Infiniti QX56 fuel gauge sender is a device that transmits data from the fuel tank to the fuel gauge. It is located in the fuel tank and attached to the fuel pump. The sender has a base with a rod and float attached to it. The float is hollow and lightweight so that it can sit on top of the fuel without sinking. The rod is attached to the base and has a rheostat meter that registers the amount of fuel in the tank.

The rheostat is an electrical instrument used to control the electrical current by varying the resistance. Inside the rheostat, there is a coil that is wound up loosely at one end and tightly at the other. The rheostat also has multiple ground connections, usually made of metal. The rod acts as a connector between the positive and ground inside the base. When the fuel tank is filled, the float moves, and the rod attached to the float moves across the coil, connecting a different resistance pattern.

The fuel gauge is designed to register the resistance of the fuel gauge sender. As the resistance is lowered all the way in the sender, the fuel gauge will register empty. As the resistance is raised, the gauge will register full.

Disconnect the battery and remove the fuel filler cap cable

Disconnecting the battery and removing the fuel filler cap cable are crucial steps in changing the fuel sender on your 2005 Infiniti QX56. Here is a detailed guide on how to perform these steps safely and effectively:

Disconnect the Battery

• Park your QX56 on a flat, level surface and ensure the vehicle is in park (for automatics) or in first gear (for manuals).
• Engage the parking brake and place wheel chocks around the front tires to prevent any accidental movement.
• Open the vehicle's hood and locate the battery.
• Identify the ground cable connected to the battery's negative post. This cable provides power to the fuel pump and sending unit.
• Using the appropriate tools, carefully loosen and remove the ground cable from the battery's negative post.
• Once the cable is disconnected, move it away from the battery to avoid accidental contact.

Remove the Fuel Filler Cap Cable

• Locate the fuel filler cap cable attached to the fuel neck. This cable is usually accessible through the fuel door.
• Carefully remove the cable from the fuel neck by unscrewing or detaching it.
• Set the cable aside in a safe place to avoid misplacing it.

Note: It is important to wear fuel-resistant gloves and take necessary safety precautions when working with fuel systems. Ensure that you have the appropriate tools and knowledge before proceeding with any repairs or modifications.

Lower the fuel tank and disconnect the harness

To lower the fuel tank and disconnect the harness, follow these steps:

Step 1: Park your Infiniti QX56 on a flat, hard surface and ensure the transmission is in park (for automatics) or in first gear (for manuals).

Step 2: Place wheel chocks around the front tires, as the rear of the vehicle will be lifted. Engage the parking brake to prevent the rear tires from moving.

Step 3: Optionally, install a nine-volt battery saver into the cigarette lighter to keep your computer live and maintain current settings.

Step 4: Disconnect the battery by opening the vehicle's hood and removing the ground cable from the battery's negative post, disabling power to the fuel pump and sending unit.

Step 5: Raise the vehicle using a jack, lifting at specified jacking points until the wheels are off the ground.

Step 6: Place jack stands under the jacking points and lower the vehicle onto them. For modern cars, the jacking points are typically on the pinch weld just under the doors along the bottom of the car.

Step 7: Remove the fuel filler cap cable from the fuel neck and set it aside. Open the fuel door to access the fuel filler neck.

Step 8: Locate the fuel tank under the vehicle.

Step 9: Using a transmission jack or similar, lower the fuel tank slightly and loosen and remove the straps securing it.

Step 10: Disconnect the harness from the connector. Feel for the harness attached to the tank, which is for the fuel pump or sending unit on older vehicles. Reach up on top of the fuel tank to access it.

Step 11: Lower the fuel tank further to access the vent hose. Remove the clamp and small vent hose for additional clearance if needed.

Note: Vehicles from 1996 onwards may have a return fuel charcoal canister attached to the vent hose to collect fuel vapors for emissions.

Now that the fuel tank has been lowered, and the harness disconnected, you can proceed to remove the fuel tank and replace the fuel sender as required.

Remove the old fuel sender and clean the mounting area

To remove the old fuel sender, you will need a flathead screwdriver, fuel-resistant gloves, a ratchet with metric and standard sockets, and a transmission jack or similar jack. Follow these steps:

• Park your vehicle on a flat, hard surface and ensure that the transmission is in park (for automatics) or in first gear (for manuals).
• Place wheel chocks around the front tires and engage the parking brake.
• Disconnect the battery by removing the ground cable from the negative post, disabling the power to the fuel pump and sending unit.
• Lift the vehicle at the specified jacking points until the wheels are off the ground.
• Place jack stands under the jacking points and lower the vehicle onto them.
• Remove the fuel filler cap cable from the fuel neck and open the fuel door to access the fuel filler neck.
• Remove the mounting screws or bolts attached to the cutaway.
• Locate the fuel tank and use the transmission jack to lower it slightly.
• Loosen and remove the straps to the fuel tank.
• Disconnect the harness from the connector by reaching up on top of the fuel tank.
• Lower the fuel tank further to access the vent hose. Remove the clamp and small vent hose.
• Remove the fuel filler neck by twisting it out of the rubber hose and guiding it out of the area. Remove the clamp on the rubber hose.
• Take the fuel tank out of the vehicle, ensuring that you transfer any fuel out of the tank first.
• Clean the harness on the vehicle and the connector to the fuel pump or sending unit on the fuel tank using electrical cleaner and a lint-free cloth.
• Remove the mounting bolts to the fuel pump and sender. You may need to rotate the fuel sender to get the float out of the fuel tank.

Now that the old fuel sender has been removed, it is important to clean the mounting area before installing the new one. Use a lint-free cloth to wipe down the mounting area and ensure that it is free of any dirt, debris, or residue. This step is crucial to ensure a proper seal and prevent leaks when the new fuel sender is installed.

Once the mounting area is clean, you can proceed with installing the new fuel sender and fuel pump, following the manufacturer's instructions or a reliable online guide.

Install the new fuel sender and tighten the bolts

To install the new fuel sender, first, install a new rubber gasket on the fuel tank. Then, place the new fuel sender into the fuel tank. Next, install the mounting bolts to the fuel pump and sender. Tighten the bolts by hand until they are hand-tight, then give them an extra turn of approximately 1/8th.

After this, place the fuel tank back under the vehicle. Wipe the rubber hose on the fuel tank with a lint-free cloth. Then, take the fuel filler neck and twist it into the rubber hose. Place a new clamp on the hose and tighten it until the slack is removed. Ensure that the clamp does not move while you are tightening.

Now, raise the fuel tank to the vent hose. Attach the vent hose using a new clamp and tighten it until the hose will not twist. Then, give the clamp an extra turn of 1/8th. Make sure that you do not use the old clamps, as they will not hold tight and will cause a vapour leak.

Next, raise the fuel tank to align the fuel filler neck with the cutaway. Align the mounting holes and lower the fuel tank. Tighten the clamp and ensure that the fuel filler neck does not move.

Now, raise the fuel tank to the harness. Connect the fuel pump or sending unit harness to the fuel tank connector. Attach the fuel tank straps and tighten them until they stop. Torque the mounting nuts to the specifications on the fuel tank. If you do not know the torque value, you can tighten the nuts 1/8th of a turn more with thread locker.

Finally, align the fuel filler neck with the cutaway in the fuel door area. Install the mounting screws or bolts into the neck and secure them tightly. Attach the cable of the fuel filler cap to the neck. Screw on the fuel filler cap until it locks in place.

Reattach the fuel tank and check for leaks

Once you have finished replacing the fuel sender, you will need to reattach the fuel tank and check for leaks. This is a critical step to ensure that your vehicle is safe to drive and that you don't lose any fuel.

First, place the fuel tank back under the vehicle. Wipe out the rubber hose on the fuel tank with a lint-free cloth. Then, attach the fuel filler neck to the rubber hose. Put the clamp in place and tighten it up, allowing the fuel filler neck to twist but not the clamp.

Next, raise the fuel tank to align the vent hose. Attach the vent hose using a new clamp and tighten it until the hose will not twist. Make sure you do not use the old clamps, as they will not hold tight and cause a vapor leak.

Now, raise the fuel tank up to align the fuel filler neck with the cutaway. Tighten the clamp and keep the fuel filler neck from moving. Then, raise the fuel tank up to the harness and connect the fuel pump or sending unit harness to the tank connector.

Finally, attach the fuel tank straps and tighten them until they stop. Torque the mounting nuts to the specifications on the fuel tank. If you do not know the torque value, you can tighten the nuts with an additional turn with thread locker.

After completing these steps, you can check for leaks. Get a transfer tank or a portable fuel can and remove the fuel filler cap. Empty the fuel into the fuel filler neck to fill up the tank. Try not to spill any fuel on the ground or neck area.

Wait 15 minutes away from the vehicle, then come back and check for leaks. Look under the vehicle for any fuel drops and sniff for any vapors. You can also use a combustible gas detector to check for vapor leaks that you cannot smell. If there are no leaks, you can continue with the remaining steps to restore your car to normal.

Frequently asked questions