10 Signs of a Bad Fuel Pump

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signs of a bad fuel pump

Last winter it happened with a close friend. He was trying to start his car in the morning and it wouldn’t respond at all. After some time when he was finally able to start his car, a loud whining noise was coming from the engine.

He instantly noticed this noise and tried to troubleshoot the problem himself. He narrowed down that the noise was coming from the fuel delivery system, somewhere near to the fuel pump.

To be certain he took his car to the mechanic. Who told him that his fuel pump might have gone bad.

What is a Fuel Pump?

fuel pump inspection

A fuel pump is a simple mechanical device that transfers fuel from the fuel tank to the carburetor or fuel injector. Fuel pressure is a critical consideration in the fuel system. The function of this pump is to deliver enough fuel to keep the fuel pressure above a certain level.

If we see it simply then the fuel pump is nothing but a regular pump. It increases the pressure of fuel as the mechanical energy on the shaft is used to increase the velocity of the fluid (fuel in this case).

How Does a Fuel Pump Work?

A fuel pump works like any other positive displacement pump. It has a narrow opening in the center. Fuel that is present in the gas tank is injected into the pump via this opening. The pump works on this fuel and increases the fuel pressure.

This pressurized fuel is delivered into the fuel line and from the fuel line, it moves to the fuel rail. From where it is injected into the combustion chamber via fuel injectors.

Where is the Fuel Pump Located?

In older cars, a gas pump was present under the hood along with other engine components. But in modern Vehicles, the fuel pump is located inside the gas tank or it is in the fuel lines. Where it draws the required amount of gas from the tank and delivers it forward.

What are the main types of Fuel Pumps?

Basically, all fuel pumps are positive displacement pumps but based upon their location and the kind of fuel system it is a part of, people have divided them into two categories.

Simple Mechanical Pumps

Pumps that are not connected to the ECU of the car directly are called simple mechanical pumps. They have simple plungers or diaphragms that deliver pressurized fuel to the carburetor.

Modern Electrical Pumps

The fuel pump motor in this type of pump is connected to the ECU of the car. It controls the working parameters of the pump. Instead of under the hood, these pumps are present in line with the fuel system or inside the fuel tank.

Signs of a Bad Fuel Pump

These are the following symptoms of a bad fuel pump:

  1. Loud Whining Sound From Fuel Tank
  2. Check Engine Light
  3. Engine Sputtering
  4. Car Taking Longer To Start
  5. Underpowered Feeling
  6. Empty Fuel Tank
  7. Stalling of Engine
  8. High Emission Rates
  9. Sluggish Acceleration
  10. Increased Engine Temperature

Let us take a closer look at the symptoms of a failing fuel pump:

1. Loud Whining Sound From Fuel Tank

Most fuel pumps will give a clear whining sound if they are not working properly. As pumps tend to have a number of rotary components, so their working is compromised if any part is not in fine condition. A bad bearing, a bad plunger, or a bad diaphragm can give a whining noise.

Hence, when you hear a loud whining noise coming out of the fuel tank then it is time to get a new fuel pump.

2. Check Engine Light

A fuel pressure gauge is installed in the fuel line. In the case of a failing pump, the fuel pressure will be dropped. The fuel pressure gauge will relay this information to the ECU of the car.

And you will get a check engine light on your dashboard. Though there are a number of other issues in the car or engine that can give you the check engine light, still it is a symptom of a failing fuel pump.

The best part about this symptom is that you would get it while you can still repair your fuel pump. Other symptoms are revealed when the problem has progressed beyond repair.

3. Engine Sputtering

Faulty fuel pumps can cause engines to sputter in an abnormal fashion. As fuel pumps are dynamic components instead of static so they give a certain level of vibration and noise when they are working.

In case if the normal operation of your vehicle’s pump is compromised you would get a sputtering engine. Moreover, in the absence of adequate fuel, engines tend to lose power.

4. Car Taking Longer To Start

Almost every component of the fuel system gives this symptom if it goes bad. Since starting of a car involves spark plugs, ignition coils, and every component that is a part of the fuel supply chain.

The fuel pump is at the head of the fuel delivery system. Even if all sensors, injectors, and rails are working fine but the part that is solely responsible for moving the fluid is not working then the car won’t start.

A fuel pump may deliver excess fuel. Even in this case, you might experience the no start situation.

5. Underpowered Feeling

If the constant stream of fuel supply is disrupted you may feel like your car is losing power. When you press the gas pedal, the car won’t respond. Especially when you are driving uphill the car would feel underpowered.

You can install a 1,000 hp engine in your car but eventually, it is the fuel that generates power in that engine. If your vehicle’s fuel pump is supplying more fuel or less fuel then this underpowered feeling is bound to come.

6. Empty Fuel Tank

A failed pump can increase the amount of fuel to the engine. This would mean a lower than usual gas mileage for your car.

A huge amount of fuel is lost to the exhaust that has other side effects as well. But with growing gas prices every now and then this issue of decreased gas mileage can really hurt you.

So, if you feel that your car is consuming way too much fuel then the fuel pump may be faulty.

7. Stalling of Engine

If the proper amount of fuel is not delivered from the tank to the engine, you might experience stalling. To deal with this issue of stalling you can try to get your fuel injectors cleaned. But if this issue is persistent then something is wrong with your fuel pump.

When you try to go at high speeds with a heavy load, the bad fuel pump will not allow you to do so. The engine starts stalling and eventually car dies.

8. High Emission Rates

A defective fuel pump may also increase the emission rates of your engine. Most modern vehicles employ a catalytic converter to decrease emission rates.

But a failed fuel pump can deliver higher amounts of fuel. This more fuel may remain unburnt during the engine cycle. The unburnt fuel will end up in the exhaust system.

The exhaust system will not be able to process it. As a result, harmful gases are released into the atmosphere.

9. Sluggish Acceleration

A bad pump can also cause sluggish acceleration of your vehicle. The reason again is the inconsistent supply of fuel. Too much or too little fuel will lead to incomplete combustion.

The amount of power produced as a result of this incomplete combustion is on the lower side. Due to which you can experience sluggish acceleration.

10. Increased Engine Temperature

High temperatures of the engine can be caused by a bad fuel pump as well. As the motor of the pump draws power from the engine shaft. In the case of a failing fuel pump, the amount of power drawn from the engine is increased. Hence, more stress on the engine. This increases the temperature of the engine.

Fuel Pump Replacement Cost

Replacement of a fuel pump can cost you somewhere between $250 and $1,100 depending upon the make and model of your car. It is possible that you won’t need a complete replacement of the fuel pump rather a bearing or rotor needs replacing. In which case the cost of replacement is decreased.

Cost of a Fuel Pump

The fuel pump itself is a costly part with prices ranging between $600 and $900. Associated parts like relay, bearings, and seals will cost you another $100 or $200.

Labor Cost for Fuel Pump Replacement

The labor cost for fuel replacement is between $150 and $250. It takes about a couple of hours to replace a faulty fuel pump. So, it is only justified to charge this much for its replacement.

Can You Replace a Fuel Pump Yourself?

You can, but I would highly advise against it. The replacement of the fuel pump is a very sophisticated procedure. It must be carried out by a professional mechanic. Moreover, anything that has to do with fuel requires extra care.

Tips to Keep Fuel Pump Healthy

By following some simple tips you can prolong the lifespan of your vehicle’s fuel pump:

  1. Don’t drive your car on low fuel very often. When the fuel is near the end, the pump has to work extra in order to deliver it from the fuel tank to the engine. Due to which its part will wear more frequently.
  2. Keep the fuel lines clean and especially replace your fuel filter once in while. Clogged fuel filters can put unnecessary pressure on fuel pumps. Hence, the chances of failure are amplified.
  3. Make sure that the quality of the fuel you are using is good. As contaminated fuel can also damage the parts of the fuel pump.
  4. Overheating of cars must be avoided at all costs. Excessive exposure to high temperatures is bad for any component of the engine.


Among other pumps of the car fuel pump is also there. Its function is very important and cannot be substituted by any other component.

From proper starting to running, and shutting off the engine you need a healthy gasoline pump.

The clearest signal a failing fuel pump gives is the whining noise from the engine. Or you might hear this sound from the fuel tank as well depending upon the location of your fuel pump.

You must combine these symptoms with others like bad gas mileage, sluggish acceleration, and increased engine temperature. Only then you can get to the bottom of this issue and diagnose that the fuel pump has gone bad.

Many people ask that why does a fuel pump fails. Well, it is a regular mechanical machine it has components that will eventually wear out.

These worn-out components need immediate replacing otherwise be ready to deal with a failed gas pump.

Frequently Asked Questions

How long can you drive with a faulty fuel pump?

You can drive approximately 5,000 miles before the pump goes completely bad. The reason why I say this is because the fuel pump is a mechanical machine that gives clear signals before going out. The wear of components is gradual rather than instant. So, you have a lot of time when the fuel pump is failing.

Can fuel pumps be cleaned?

Yes, most fuel pumps can be cleaned. You need to remove it first, then open it completely. Certain chemicals are available in the market that are used to clean deposits from the surface of fuel pumps. But this is not the permanent solution. As you would start experiencing the above symptoms in no time again.

How do cars act when they have failing fuel pumps?

The car tends to act sluggish when they have failing fuel pumps. You would also feel powerless while accelerating the car. You will feel a stalling engine that loses power at times when you have a failing pump in your car.

Will a bad fuel pump throw a code?

Yes, bad fuel pumps can throw a code. The fuel pump itself is not a programmed component, but there are several sensors linked to it. If the amount of fuel is more or less than required these sensors will go off and throw a code.

What can happen if you have a blown fuel pump fuse?

Fuse on fuel pumps is responsible for switching them on or switching them off. If you have a blown fuse then the power supply to the motor of the fuel pump remains uninterrupted. When the engine of the car is running idle even then the same amount of fuel is being delivered.

Is the fuel filter clogged due to fuel pump failure?

Yes, failure of fuel pumps can cause fuel filters to get clogged. A bad fuel pump may not be able to clear out the debris of contaminated fuel that is clogging the filter. Healthy fuel pumps deliver fuel at high pressure that clears out any contaminants in the fuel lines. With defective fuel pumps, the pressure is not built and contaminants get stuck inside fuel filters.

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