12 Bad fuel pump symptoms

The fuel pump is probably the most important part of your vehicle. Its function is to take gas from the tank and send it to the engine. It allows your car to start and run. Because it is such an important part, fuel pumps should last you for at least 100,000 miles.


The most common symptoms of a weak, failing, or bad fuel pump are the check engine light coming on and the engine misfiring. However, other signs of a failing fuel pump are reduced power and weird acceleration.

In this article, we’ll also cover the following:

  • What makes it go bad
  • What happens when it goes bad

Continue reading

If you have already exceeded the 100,000-mile mark, there is a high chance of the fuel pump failing. When that happens, there are specific symptoms you can look for and take the necessary action to replace this component. The fuel delivery system is complex, and such an important part has to be highly valued.

Holley Blue fuel pump

For modern cars, this part is considered to be their heart. Once this pump fails, the entire vehicle will stop running, and you might also have trouble starting it up again. This article will look at 12 bad, failing & weak fuel pump symptoms so you can make troubleshooting easier. 

Table of Contents

What does a fuel pump do?

This part sends gas directly to the engine, which makes it a vital part of your vehicle. This process is simple but essential. The gasoline will pass through a fuel filter to reach the injectors and finish by combusting inside the cylinders. 

Without this pump, fuel would have no way to reach the engine, and the pistons would have difficulty delivering power. In some older vehicles, mechanical fuel pumps use complex diaphragms to transport the fuel to the engine. 

Modern cars have electric fuel pumps mounted inside the gas tank. These ones are also safer because they reduce fire risk. Since they are installed far from the engine, they often work independently. 

If this part is failing, it is crucial to change it as soon as possible, as your vehicle might represent a real danger for other drivers. Your car will not work properly without this component.

Symptoms of a bad, failing, & weak fuel pump

There are several symptoms that will tell you if the fuel pump is bad, failing, or weak. We found the most common 12 ones, so pay attention and notice if you can identify some of them in your vehicle.

fuel pump

Let’s take a look at some of the signs:

  • Increased fuel consumption
  • Loss of power
  • Fluctuating engine speed

1. The check engine light comes on.

This light will appear on your dashboard once you have fuel pump issues. Most likely, your car has already started running weirdly. It lacks the smoothness you were used to. 

Use the check engine light as a final confirmation that something is wrong with the component. A specialized mechanic will be able to diagnose your vehicle and recommend replacement parts.

2.Increased fuel consumption

When this component is failing, the engine might consume more fuel. You should notice this after driving for a while. You will know the difference between your average consumption and the new one. 

In this case, you might want to check the entire fuel system. Take your car to an auto repair shop and have the experts take a look at it. 

Fuel pump for Ford

3. The car struggles to climb a hill.

If you live in an area with hills, you are most likely used to having your car climb them effortlessly. When this part is failing, the entire performance of your car is reduced. You will notice this, especially when you are driving uphill.

4. Reduced power

Because there is not enough gas supplied to the engine, the power will be reduced. It means you might lose the ability to reach and maintain a stable high speed. On a highway, this can be dangerous.

Pull over to the side and call for help, as your vehicle is now a danger to other drivers. 

5. Engine speed fluctuates

Because the gas delivery is uneven, the performance of your engine will fluctuate. The car will want to accelerate and slow down shortly after while constantly repeating this cycle. On a highway, it can be extremely dangerous.

6. Acceleration is hesitant

Under normal circumstances, your car should be able to accelerate quickly from a full stop. An instant response is necessary, especially on a busy street or when you merge into traffic. 

But if your fuel pump is failing, you might experience a delayed response when you step on the gas. 

7. The engine is misfiring.

Often, you will feel misfires rather than hear them. They will feel like your car is bumping a lot, and it is clearly an indication that there is something wrong. Misfires will eventually damage your engine, so you should replace this part as soon as possible.

Fuel pump for Ford Diesel

8. Rough running at low speed

If rough running occurs only once, it is not something to worry about. But if this problem occurs frequently, you should start investigating and consider this part as a possible cause.

9. The engine suddenly stalls.

Sometimes your engine suddenly stops, and you can’t explain why. It can be annoying and incredibly dangerous if it happens on the road. You should fix this problem as soon as possible.

10. You can’t start the car.

As you turn the key or push the start button, nothing happens. Sometimes cranking the engine takes longer than you expected. In this case, a starting failure clearly indicates a failing fuel pump. 

2011-2016 Duramax Fuel Pump

11. Overheating engine

Your car’s engine might overheat for various reasons, and a malfunctioning fuel pump is one of them. It happens because the bad pump incorrectly delivers gas to the engine, causing it to run too hot.

12. Low fuel pressure

Test your fuel pressure to determine the cause of a failing pump. You can do this with a pressure gauge found at any auto shop. Find the recommended pressure of your vehicle in its owner manual. Compare the result with the indication provided by the manufacturer. 

Bad fuel pump relay symptoms

Cp4 Fuel Pump Off 2011 Duramax

Many processes take place when you turn the key in your car. One of them is the vehicle’s ECM sending a signal to this part, commanding it to put a specific amount of gas to start your engine. It is done with the help of the fuel pump relay.

When this relay gets powered, it sends the signal to the pump. When it malfunctions, it automatically switches off. This component cannot work properly. There are 5 symptoms you should look for in a bad pump relay, and they are:

  • The engine is stalling
  • There is no noise from this part
  • Check engine light comes on the dashboard
  • You cannot start the vehicle
  • Rough acceleration

What happens when if it goes out while driving?

If this part goes out while driving, the car will most likely turn off. You will have to pull over to the side of the road and call a car towing service. If you have an older diesel engine, you can still drive a few miles with a faulty system, but it might be difficult. 

Rolling at a low speed and avoiding steep hills might let you reach the next town. But fuel-injected gasoline engines will stop functioning entirely, and you might have to spend the night on the highway. Without gas running through them, these engines cannot function.

Here are some of the biggest fuel pump manufacturers in the space.

BoschStuttgart, Germany
ContinentalHanover, Germany
DelphiGillingham, United Kingdom
DensoKariya, Japan
WalbroCass City, Michigan, USA

How does a car act when it is going out?

Bmw n54 high pressure fuel pump

When this part goes out, the car will show various signs. For example, a damaged fuel pump might make a loud noise coming from the gas tank. But this sound can also occur if you are low on fuel or the fuel itself is contaminated. 

Additionally, you might struggle to start your car. This part cannot push enough gas to the engine, preventing it from starting. You will notice a different performance if you still manage to start it. Your engine will sputter and stall. 

What causes it to go bad?

There are many causes of a bad pump. The most common ones include contamination, overheating, and the part itself wearing out over time. Another cause is:

  • rust
  • debris
  • and dirt particles that clog up your pump filter.

With time, it is making the pump harder to operate efficiently.

This part has many components inside, and these particles will stress and accelerate their wear. Next time you refuel your vehicle, make sure the gas pump is pushing no particles in your car’s tank to avoid a clogged pump.  

Here’s what you can expect to pay depending on the issue you’re facing.

Wear and Tear on the Pump$200 – $800
Clogged Fuel Filter$50 – $150
Faulty Electrical Connections$100 – $300
Contamination in the Fuel Tank$150 – $600
Damage to the Fuel Pump Relay or Fuse$100 – $300
Replacement of the Fuel Pump$500 – $1000
APR high pressure fuel pump with parts

How to check there are issues

You can start by checking the relay. In older fuel systems, the engine doesn’t control this component directly. Instead, it uses a relay. If this relay is broken, this part will stop working. 

If the relay is functional, check the fuel pressure regulator. On a continuous system, disconnect the attached vacuum hose and see if the pressure increases on the regulator. The regulator is faulty if the pressure does not increase.

Fuel pumps have an external filter that is very easy to install. Instead of testing it, you should install a new one and see if your problem is fixed. Before replacing the filter, relieve the fuel system pressure while wearing adequate safety equipment.

Bmw fuel pump

What if it is new & has issues?

Gas contamination is one of the most common causes of fuel pump failure. With corrosion, debris, and moisture, fuel is ruined and will bring contaminants into the tank. These contaminants will eventually clog essential components, filters, or even the pump itself.

This blockage will stop the fuel flow, making it difficult for your vehicle to accelerate or run properly. At the same time, electrical faults are also responsible for pump failures. Rusted connectors or melted wirings can stop the pump from functioning properly. 

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