7 Indications of a Bad Fuel Pump and How to Fix Them

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Car dashboard with warning lights indicating a bad fuel pump

How often do you think about your fuel pump? Fuel pumps inject gasoline from the fuel tank to the engine in most cars and trucks. Your vehicle can’t function without a working fuel pump; if it stops working, it stops driving. Almost all modern vehicles have electric fuel pumps mounted on their fuel tanks, and others have inline or mechanical pumps. Because the fuel pump is responsible for supplying the engine with fuel, any issues will lead to significant performance problems and potentially expensive auto repairs. Eventually, most fuel pumps in vehicles will need to be replaced.

How to Diagnose a Bad Fuel Pump

As a professional car mechanic with over 15 years of experience, I have dealt with my fair share of bad fuel pumps. I remember a customer complaining about their engine sputtering and losing power, only to find out that their fuel pump was the culprit. Another time, a car could not accelerate and significantly decreased gas mileage, which turned out to be caused by a bad fuel pump. Over the years, I have fixed countless fuel pumps and have learned that the signs of a bad fuel pump, such as engine sputtering, decreased fuel pressure, power loss, and an inability to accelerate, are usually consistent.

1. Engine Sputtering

A car engine with visible smoke and distress.

If you drive at high speeds and your engine starts to sputter, it is likely due to a failing fuel pump. A bad fuel pump can cause your vehicle to sputter and then suddenly chug back to regular performance. Sputtering happens when the fuel pump struggles to supply constant fuel to the engine, resulting in a choppy ride. If you notice these symptoms, having your fuel pump checked out by a mechanic as soon as possible is best.

2. Fuel Tank Noise

If you hear a loud, whining sound coming from your gas tank, it’s important to get it checked out, as it could be a sign of a damaged fuel pump. A failing fuel pump can cause many issues with your vehicle, including stalling, poor acceleration, and difficulty starting. Suppose you notice any issues with your fuel pump or hear unusual sounds from your tank. In that case, it’s best to have it inspected by a professional mechanic as soon as possible to avoid further damage or safety hazards.

3. Loss In Fuel Pressure

If your check engine light is on and your car is stalling, your fuel pump is likely faulty. Low fuel pressure can cause acceleration issues, rough idling, engine stalling, and other problems, typically linked to a malfunctioning fuel pump. It’s important to get this issue checked and fixed as soon as possible to ensure your car runs smoothly and safely.

4. Loss of Power

If your vehicle struggles while climbing a hill or carrying heavy cargo, it could indicate a problem with the fuel pump. When your car is under stress, the fuel pump may not be strong enough to meet driving demands. Any loss of power during acceleration may be a sign of a fuel pump issue, which should be addressed promptly to avoid further damage to your vehicle.

5. Inability To Accelerate

A bad fuel pump can cause irregular resistance within the fuel pump motor, which can decrease your car’s speed or make it unable to accelerate at all. If you experience these symptoms, your fuel pump likely needs inspection. A loss of engine power is another sign that your fuel pump may fail and must be replaced.

6. Decreased Gas Mileage

A bad fuel pump can cause multiple issues in your car, such as a significant decrease in fuel efficiency. If you observe a sudden drop in your car’s fuel mileage, it could indicate a faulty fuel pump. The relief valve in the fuel pump allows a regulated flow of fuel to the engine system, but if it fails to open, more fuel than necessary can flow into the engine system, causing you to refuel your car more frequently. This alone is a good enough reason to replace your fuel pump, as a car chugging gas will be more expensive to run in the long term.

7. Engine Not Starting At All

If you ignore any of the issues mentioned above, it will inevitably lead to a complete malfunction of the fuel pump. This will result in the engine not receiving any fuel, which in turn will cause your car to fail to start. While there could be other factors at play, diagnosing a fuel pump issue is usually the result of one or more of the problems as mentioned earlier.

How to Fix a Damaged Fuel Pump

Mechanic repairing a damaged fuel pump with tools and parts

Repairing your car’s fuel pump is crucial to ensure it functions correctly. Suppose you notice any signs of malfunction, such as a decrease in fuel efficiency, difficulty starting your car, or strange noises. In that case, taking action immediately is essential to avoid further damage. While it may be expensive to get it fixed by a professional, you may be able to repair or replace it yourself. However, it’s important to follow the proper steps and safety precautions to avoid any accidents or damage to your vehicle.

  1. Disconnect the negative battery cable in your engine.
  2. With a safe workspace at hand and your car parked on a level surface, jack it up or place it on a lift to access the underside of your vehicle.
  3. Relieve the fuel system pressure (this is different depending on the make and model of your vehicle, and you’ll want to Google this or consult your service manual).
  4. Disconnect the filler neck from the fuel tank.
  5. Support the fuel tank via the jack and block of wood.
  6. Remove the bolts from the straps that hold the fuel tank in the vehicle.
  7. Very carefully disconnect all wiring connections, fuel lines, and vent hoses on the top of the tank before lowering the tank (as this will probably spill gasoline and oil, be careful).
  8. Once you release the connections, use the jack to lower the tank out of the car.
  9. Clean the top of the tank around the existing fuel pump assembly to prevent any debris from falling into the tank.
  10. Refer to your service manual for all instructions on removing the fuel pump assembly from the tank, which typically includes removing a plate held in with screws or bolts.
  11. Install the new pump in the opposite order you removed the old one (Reconnect the fuel lines, wiring connections, vent tubes, and battery cable).  Don’t forget to check the oil pressure in case you have spilled more.
  12. Fill the tank with gas and take your vehicle for a drive to ensure you’ve properly replaced the fuel pump and everything is working.

If you find this process intimidating, contact your local auto parts store, dealership, or auto mechanic and have them help you or take care of the fuel pump issue entirely. Once you fix or replace your fuel pump, your vehicle should enjoy many more years of service.


With the knowledge of the seven telltale signs of a bad fuel pump and the steps to remedy this critical issue, you are now equipped to tackle one of the most common yet often overlooked vehicle maintenance challenges. Remember, the fuel pump is the heart of your vehicle’s engine, pumping vitality to its core. Ignoring these signs is like neglecting your vehicle’s health, which can lead to a cascade of performance issues or, worse, leave you stranded. Whether you’re a seasoned DIY enthusiast ready to undertake a fuel pump repair or someone who prefers the expertise of a professional mechanic, taking prompt action at the first hint of trouble can save you time, money, and the inconvenience of major automotive failures. So, rev up your maintenance routine, and ensure your ride remains smooth, efficient, and most importantly, operational. After all, in the vast journey of automotive care, staying informed and proactive is the key to enduring performance and reliability. Let this guide be your roadmap to navigating the complexities of fuel pump maintenance, empowering you to drive confidently into the future.

FAQs About Fuel Pump

How do you know your fuel pump is faulty?

Signs of a faulty fuel pump include engine sputtering at high speeds, a whining noise from the fuel tank, decreased fuel pressure resulting in loss of power or inability to accelerate, unexpected drops in gas mileage, and the engine not starting. Each of these symptoms can indicate that your fuel pump is not functioning properly.

How can I test my fuel pump?

To test your fuel pump, start by checking the fuel pressure with a fuel pressure gauge. Connect the gauge to the fuel pump test point, which is usually found on the fuel rail. Turn the ignition on and observe the pressure reading; it should match the specifications listed in your vehicle’s repair manual. Additionally, listening to the fuel pump’s operation when you turn the key to the “on” position (without starting the engine) can indicate whether it’s working. No sound may suggest a malfunction.

Does the fuel pump give a warning before going out?

Fuel pumps can show several warning signs before failing completely, including engine sputtering, loss of power under stress, unusual noises from the fuel tank area, and difficulty starting the vehicle. However, in some cases, a fuel pump can fail suddenly without warning, especially if it’s due to an electrical fault.

What does a bad fuel pump sound like?

A bad fuel pump often produces a loud whining or buzzing noise from the fuel tank area. This sound can be more noticeable when starting the car or when fuel levels are low. It’s caused by the pump struggling to deliver fuel at the correct pressure due to wear or damage.

What is the most common cause of fuel pump failure?

The most common cause of fuel pump failure is contamination within the fuel system. Dirt, debris, or rust can enter the fuel tank and get caught in the pump, leading to wear and tear. Additionally, consistently running your vehicle on a low fuel tank can cause the pump to overheat and fail, as the fuel acts as a coolant for the pump motor.

Can a bad fuel pump damage the engine?

While a bad fuel pump itself doesn’t directly damage the engine, it can lead to situations that might. Insufficient fuel supply can cause the engine to run lean (too much air in the fuel-air mixture), leading to overheating and increased wear on engine components. This can eventually cause engine damage if not addressed.

Can a bad fuel pump cause high fuel consumption?

Yes, a malfunctioning fuel pump can cause high fuel consumption. If the pump’s pressure relief valve fails to open, it can allow more fuel than necessary into the engine system, leading to inefficient combustion and increased fuel usage.