10 Symptoms of a Bad Fuel Pump

The fuel pump in your car delivers gas from the gas tank to the engine so your car can run smoothly. If the pump overheats becomes damaged, or fails, the car’s engine won’t get the fuel to run properly or at all. If you notice these ten signs, consider taking your car to your local dealership to have the fuel pump replaced.

What Is A Fuel Pump And How Does It Work?

A fuel pump is a small electric motor that transfers fuel from the tank to the engine. In older vehicles, the fuel pump is mounted along the frame rail, and fastened into the fuel line. Classic cars often use a mechanical fuel pump at the engine that pulls fuel to the front of the car rather than a pump at the back, pushing it forward. 

Modern cars almost all have a fuel pump inside the fuel tank. The small cylindrical pump is part of a larger assembly that includes a fuel level sensor and a fuel filter screen. Generally, pumps can produce more pressure by pushing fluid through the line rather than drawing it up. 

A fuel pump for today’s engines usually uses an impeller-style system that pulls fuel through it, creating positive pressure on the engine side of the pump. Other styles including a rotary vane and gerotor pump are available for select models, but they’re far less common. 

Once the pump has built pressure, it’s intended to hold it by preventing fuel from bleeding back into the tank. In this way, there’s always fuel in the line, primed, so you can start your engine quickly whenever you need to.

bad fuel pump symptoms

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Signs of a Bad Fuel Pump

If your car is experiencing any of these bad fuel pump symptoms, bring it in for a vehicle checkup!

#1. Whining Noise from The Fuel Tank.

One of the first symptoms of a problem with the fuel pump is a loud whining sound. An old or worn fuel pump may produce a noticeably loud whine or howl while running.

Most fuel pumps will produce a quiet hum during their normal operation, however, an excessively loud whine coming from the fuel tank is usually a sign of a problem. There may not be enough fuel, a damaged pump, or contaminated fuel inside the system.

#2. Difficulty Starting.

Another symptom commonly associated with a problematic fuel pump is difficulty starting. Because fuel pumps constantly run whenever the ignition is turned on, they can eventually wear out and weaken over time.

A weak fuel pump may still pump fuel, but the vehicle may experience difficulty starting from the lack of pressure. A weakened fuel pump can cause the vehicle to take more cranks to start than normal, and in more serious cases may even cause the vehicle to require multiple turns of the key before it starts.

#3. Engine Sputtering.

One of the surest indicators of a faulty fuel pump is a sputtering engine — typically at high speeds. Should you be driving at a consistently high speed and the engine suddenly sputter before returning to normal operation, it may indicate issues within the fuel pump. In this case, the fuel pump cannot provide a constant stream of fuel to the engine at the ideal pressure.

#4. Power Loss.

Another indication of a bad fuel pump is a loss of power when the vehicle is under stress — such as driving uphill or carrying a heavy load — or while accelerating. The engine shuts down because weakening parts of the fuel pump cannot keep up with the car’s heightened fuel demands in these situations.

In these circumstances, the car will feel like it is unable to go or maintain the intended amount of power. If the fuel pump is the cause, it means it can no longer regulate fuel pressure accurately and provide the appropriate amount of fuel to the engine.

#5. Decreased Mileage.

There may be a problem with the engine if your car usually gets good gas mileage but starts guzzling it out of nowhere. If the relief valve on the fuel pump fails to open, excessive fuel will flow into the engine system. If you notice you’ve been heading to the gas station more often than normal, visit your local mechanic right away.

#6. Car Surging.

Irregular resistance inside the fuel pump motor may cause vehicle surging and indicates a fuel pump in need of repair. Surging feels like the accelerator pedal has been used. However, it occurs at a random, consistent speed. If this happens often, it may be because of problems within the fuel pump.

#7. Check Fuel Pressure.

Keep an eye on your fuel pressure gauge because it will tell you how much gas is getting to the vehicle’s engine. Have someone else rev your car while you check the gauge. Refer to your owner’s manual to see how much pressure you should expect. If it’s too low, that’s a sure sign your fuel pump is failing.

#8. Check Engine Light Comes On.

In modern cars the sensor system will detect issues with the fuel pump, notifying the ECU and resulting in the check engine light illuminating.

If the injectors don’t receive enough pressurized fuel, there may not be enough sprayed into the cylinders to be burned. A ‘P0171 System Too Lean’ code could be stored in the powertrain control module, triggering the Check Engine Light.

#9. Stalling At High Temperatures.

Stalling can happen because of multiple problems within a vehicle but pay attention when it happens frequently at high temperatures shown on the car’s thermometer. A rising temperature paired with stalling often indicates a problem with the fuel pump motor.

If stalling continues to occur with an increasing temperature gauge, it could indicate the fuel pump’s deterioration and need for replacement.

#10. Car Will Not Start.

Another more serious symptom of an issue with the fuel pump is a no-start condition. If the fuel pump fails completely — to the point of not being able to provide enough fuel for the engine to run, the vehicle will refuse to start.

The engine will still crank when the key is turned, but it will be unable to start due to the lack of fuel. A no-start situation can also be caused by a variety of other issues, so having the vehicle properly diagnosed is highly recommended.

Related Post: Top Reasons Why Your Car Won’t Start

What Happens When a Fuel Pump Goes Out?

A failing/failed fuel pump will cause major performance and drivability issues with your vehicle. If your fuel-to-air ratio is off and the cylinders aren’t getting enough fuel, then the pistons aren’t firing and your engine is struggling to move the vehicle forward. We’re not just talking about lower gas mileage or inefficiencies. If your fuel pump is bad enough, your car won’t start!

How long does a fuel pump last? Because of the important role they play, fuel pumps are meant to be tough and withstand almost the entire life of your car. You typically don’t have to replace your fuel pump until you have at least 100,000 miles on your vehicle, and fuel pumps have been known to last more than 200,000 miles!