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Assuming that you have a vehicle with an internal combustion engine, a vital part of the system is a fuel pump, which delivers fuel to the engine. The fuel pump is responsible for moving fuel from the vehicle’s fuel tank to the engine with sufficient pressure. From there, depending on your vehicle, different things can happen.

In the case of an older, carbureted vehicle, many of these pumps were mechanical and attached to the engine. They worked by pulling fuel from the tank with suction, and pressurizing it on its way to the carburetor.

In modern gasoline vehicles, this is done via an electric fuel pump located within the fuel tank, which pressurizes the fuel for use in a fuel injection system

In diesel engines, fuel is delivered via a “lift” pump, which brings fuel from the fuel tank to the diesel injection pump, which turns the lower-pressure delivery of the fuel into extremely high pressure for a diesel injector. Most lift pumps today are electrical, although a few mechanical pumps still exist.

An electric fuel is in a vast majority of the cars that are on the road today. This kind of pump turns on when you put your key in the ignition and turn to run/start. Usually, if functioning well, it sounds like a soft hum in the background of your car.

If there are any problems with your fuel pump, this becomes evident very quickly. Having a bad fuel pump can leave you stranded, so it is important to recognize the signs of a bad fuel pump and understand how much it costs to replace it.

Bad Fuel Pump Symptoms

One of the first things you might notice with a bad fuel pump is that your car sounds different when it is on. A well-functioning fuel pump generally gives off a soft humming noise when your vehicle starts up. If instead you hear a sharp whining sound from your fuel tank, then this is very likely a sign you need a new fuel pump. The first thing you should do if you hear this noise is ensure that you are not running below empty.

A second consequence of a bad fuel pump is that your car might have a difficult time starting. One of the fuel pump’s primary jobs is to keep a level of static pressure within the fuel system. This way upon startup, the pump does not need to completely re-prime the entire system again. As your fuel pump ages, it can lose the ability to keep this static pressure, causing you to have to crank your car for a considerable amount of time before start up.

A weak fuel pump is one that will often not hold sufficient pressure for the fuel injection system to operate properly. In many cases, it can start the vehicle, but acceleration can be a problem with hesitation, lack of power, or stalling. In any of these cases, a running and/or static fuel pressure test can help determine if the fuel pump is the culprit. Keep in a mind, a clogged fuel filter can exhibit some of the same “weak fuel pump” symptoms, so changing the fuel filter is always the first step. 

To properly test the fuel system, AutoZone has a fuel pressure testing kit with their Loan-A-Tool program, which saves you money and guesswork. If you’re unsure how to test or perform this, you can also search through our list of Preferred Shops in your area that can help.  

In modern vehicle fuel pumps, the pump assembly usually contains the fuel-level sending unit as well, so if your fuel gauge is not properly working, you can often trace it to a fuel pump assembly unit not functioning properly. In both cases, changing the fuel pump can rectify the issue.

Finally, you may not be able to get your car to start at all. Unfortunately, many pumps do not give any warning sign of their failure. Sometimes, a pump can die while the vehicle is on the road, and other times, the vehicle shuts off, the pump seizes, and never starts again.

Most cars have a prime cycle that the fuel pump will go through when the key is turned to on, but not start. This prime lasts usually about 3-5 seconds where you will hear the pump turn on in the tank. If you don’t hear this at the tank and have before while the car was operating properly, the fuel pump is suspect.

Fuel Pump Replacement Cost

The actual cost of replacing a fuel pump depends on several factors. The parts cost of a fuel pump is usually between $75 and $250, depending on the vehicle. If you are replacing the fuel pump yourself, beyond this it is just the cost of your time. Generally speaking, replacing a fuel pump is considered an intermediate-level task.

If you decide to go with a professional, you may be looking at a cost of between $400 and $600 to replace a bad fuel pump. You can search through our Preferred Shops in your area for a mechanic that can help with the fuel pump repair. Expect the actual replacement to take between 1 to 6 hours, depending on the expertise of the mechanic and the tools they happen to have on hand.

Whether you do the job yourself or have a professional do it, make sure that the fuel tank is properly cleaned of all contaminants, as years of fuel sediment can build up in the bottom of the fuel tank. Remember that AutoZone has all the parts and tools to tackle the job should you choose to do it on your own!

Advice, how-to guides, and car care information featured on AutoZone.com and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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