Hobbies Cars & Motorcycles How to Replace a Car's Fuel Sending Unit Share PINTEREST Email Print Daniel Grill/Getty Images Cars & Motorcycles Cars How Tos Basics Reviews Classic Cars Corvettes Mustangs Tires & Wheels Motorcycles Used Cars Trucks ATVs & Off Road Public Transportation By Matthew Wright Matthew Wright Matthew Wright has been a freelance writer and editor for over 10 years and an automotive repair professional for three decades specializing in European vintage vehicles. Learn about our Editorial Process Updated on 02/23/19 If your gas gauge has been acting up, or if you've been running out of gas on a regular basis, you might need to replace your fuel tank sending unit (also known as the fuel sender). In most cars this is a fairly straightforward process. Check your repair manual, but if your car's fuel tank sending unit is located under the rear seat or in the rear cargo area, where a large percentage of fuel senders are accessible, you're in luck. It's easy! 01 of 03 Tools You'll Need Amanda Fox/EyeEm/Getty Images Flathead screwdriverPhillips head screwdriverHammerOpen end wrenchesReplacement fuel tank sending unit 02 of 03 Getting to Your Fuel Tank Sending Unit Matt Wright Before you begin, disconnect the negative battery cable to be sure no electrical sparks are possible. You're dealing with gas, which is highly flammable! Also, be sure to roll all your windows down and work in a well-ventilated area to prevent breathing in fumes. You could also use a professional respirator. Your fuel tank sending unit is located at the top of the fuel tank, but it is accessible under your backseat (or under the carpet in your trunk). The sending unit will be protected by an access cover, usually held on with a couple of screws. Lift your backseat or trunk carpet and locate the access cover for your fuel tank sending unit. Remove the screws holding the cover in place and remove the access cover to reveal the fuel tank sending unit. Helpful Hint: Since it's almost impossible to do this job without a single drop of fuel escaping, it's a good idea to have some protection handy. Try covering part of the work area inside the car with plastic and an old towel. This area can be used as a staging area for the parts that will have gas on them. 03 of 03 Removing the Fuel Tank Sending Unit Matt Wright Another Safety Note: Gasoline is highly flammable. By removing the fuel tank sending unit, you are opening the gas tank. Be sure there are no sources of spark or flame nearby. Always do this repair outside with the windows of your vehicle rolled down. Never open your tank in a garage that could have a source of ignition, such as a furnace or water heater. With the access cover removed, you'll see the fuel tank sending unit right there on top. It will have a wiring harness plugged into the top, which tells the gas gauge how much fuel is in the tank. Unplug the wiring harness and move it safely to the side. If your fuel tank sending unit is screwed or bolted in place, remove the screws or bolts. Some sending units are a "twist-lock" type and work like the old twist-lock gas caps. You'll see a few notches along the outer ring of the sending unit. Place the tip of a sturdy, flat head screwdriver in the notch and gently tap it counter-clockwise. The sending unit will rotate until it's loose. The picture above shows the fuel tank out of the car to illustrate the fuel tank sending unit's location. Now you can remove the fuel tank sending unit in one piece. Attached to it is a long rod with a float at the end, so you might have to try a couple different angles to get it out. As usual, installation is the reverse of removal. Don't forget to plug in the new sender or it won't send you anything! If your fuel filter is in the tank at this location, it might be a good idea to replace that as well.