Symptoms of a Bad Fuel Pump | Autance

Consider the fuel pump as the heart of the modern automobile with an internal combustion engine. It would be impossible…

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Symptoms of a Bad Fuel Pump | Autance © Symptoms of a Bad Fuel Pump | Autance

Consider the fuel pump as the heart of the modern automobile with an internal combustion engine. It would be impossible to deliver fuel to the combustion chambers without this device pushing fuel through a series of hoses. A good motorist should always be able to spot some of the early signs of a bad fuel pump. This will help him or her to determine the next action to take. So what signs and symptoms should you look for that will indicate you may have a failing fuel pump?

A Look at the Fuel Pump

Let us start our discussion by answering the question, ‘what is a fuel pump?’ The name of the device is self-explanatory. It ‘pumps’ or ‘pushes’ fuel through a line. It works like an ordinary water pump. It draws fluid from one area and delivers it to another. In the modern vehicle, this translates to the movement of fuel from the fuel tank to the engine. It is the fuel pump’s job to deliver the necessary fuel from the tank to the engine.

The invention of the automobile presented different challenges to engineers and manufacturers. One of them is how they can get the fuel to go from its storage tank and straight into the engine for combustion.

The earliest models of fuel pump relied on gravity to deliver fuel to the carburetor. These are not ‘pumps’ per se because they let gravity do the work. However, with advances in automotive technology, fuel tanks relocated to the rear of the car for safety reasons. The car can no longer rely on gravity to deliver fuel to the carburetor. This brought about the invention of the mechanical fuel pump.

Fast forward to the latter part of the 20th century and you now have electronic fuel injection systems. These required a different fuel pump technology. As such, the fuel pumps we have in today’s vehicles are almost always electric pumps. These modern versions work with the fuel pump regulator to ensure greater efficiency in the delivery of fuel.

Check Out Our Review of Fuel Transfer Pumps

Symptoms of a Bad Fuel Pump

Regardless of the type of fuel pump that your vehicle has, it will still manifest almost the same bad fuel pump symptoms. Here’s a look at the more common manifestations of an impending fuel pump failure.

  • Whining noise coming from the gas tank

This is one of the earliest signs of a bad fuel pump. Unfortunately, not many vehicle owners can distinguish the difference between a whining noise coming from the engine and one from the fuel tank. A normal pump will produce a clicking sound once you crank up the engine. As you drive, the sound will turn into a quiet hum.

If you hear a loud whining noise coming from the car’s fuel tank, there is a chance that you may already have a failing fuel pump. This is not the only reason, of course. It is also possible that the tank does not have enough fuel. Contaminated fuel can also produce a whining sound from the tank.

  • Engine sputtering

This is one of the surest signs of fuel pump failure. It is the job of the pump to deliver fuel from the tank to the engine at all times. If you are driving at a normal speed, then the pump may still be able to deliver enough gas to the engine. You will not notice any sudden drop in engine performance. If you drive at a high speed, there is a chance that the pump may not be able to supply the right amounts of fuel to the engine. This can lead to engine sputtering.

One way you can be sure about this is to go for a test drive. Drive your car at high speeds until you notice sputtering from your engine. Once you notice this, decelerate to normal driving speeds. The sputtering should disappear. This indicates that the fuel pump is able to deliver gasoline to the engine when the engine is not overworked.

  • Difficulty starting the engine

Fuel pumps are also subject to normal wear over time. It can also weaken and compromise its ability to deliver fuel. It can still pump fuel. However, it may not be at the right fuel pressure. When you start your engine early in the morning, the pump will push fuel to the combustion chambers. This will initiate the combustion process.

A weak fuel pump will only be able to deliver minute amounts of fuel at a time. You will notice that it will take you a number of times to crank the engine before it turns over. The pump will deliver minute amounts of fuel with each crank of the engine. After some time, enough fuel builds up and starts the engine. There may be other explanations as to why you have difficulty starting the engine. However, one should never overlook the possibility of fuel pump failure if you also notice other symptoms.

  • Stalling when the engine reaches high temperatures

Clogged fuel injectors can cause your engine to stall. So does the presence of water in fuel. Problems with the camshaft position sensor or the crankshaft can also lead to engine stalling. The mass air flow sensor or the air intake temperature sensor can also be problematic. A faulty ignition coil can also result to engine stalling. However, one should always entertain the possibility of a failing fuel pump as the reason for stalling.

There is one way you can differentiate this cause from other causes. If the stalling occurs only when the engine reaches its highest temperature, then you can suspect a problem with the fuel pump. If the engine is not receiving enough fuel, it will try to work harder. This will lead to an increase in its operating temperature.

  • Loss of or reduced engine power under stress

Driving uphill will make your engine work harder. Hence, it will need more fuel. The same is true when carrying or towing a heavy load. The engine will have to work more to help move the vehicle against these resistance forces. The engine will also work harder during hard acceleration. It needs more fuel to help push the vehicle from a gentle cruise to high speeds. This should not be an issue if your fuel pump is working fine.

An engine that shows reduced power or loses power when driving in these conditions may signal the presence of a failing fuel pump. You will not see these bad fuel pump symptoms when driving in normal conditions. The mere fact that the engine needs to work harder signifies that it needs more fuel. Unfortunately, a bad pump may not deliver the extra fuel that the engine needs in high-power conditions. As such, you will notice a drop or loss in engine power.

  • Poor fuel economy

There are many potential causes of poor fuel economy. One of them is a defective relief valve in the fuel pump. If the valve fails to open properly when it should, it causes fuel to flow in a continuous manner to the engine system. It is important to realize that the engine needs only very precise amounts of fuel. If there is too much fuel in the engine system, this fuel will not get used. It will also not get stored. As such, it will be a waste.

Other potential causes of poor fuel economy include a failing thermostat, worn spark plugs, or inaccurate coolant sensor. Sluggish oxygen sensors and EGR valve leaks can also lead to poor fuel economy. It would be best to have a mechanic check your car to help determine the exact cause of poor fuel economy.

  • Surging

You are driving at a normal, constant speed. All of a sudden, you feel a sudden surge in engine power. This makes the car accelerate in a random manner without stepping on the gas pedal. This is the kind of car surging that mechanics associate with a failing fuel pump.

The most plausible explanation for this symptom is the presence of irregular resistance within the pump itself. The pump operates by providing consistent pressure to deliver the fuel to the engine. If there is a change in the resistance, then more fuel gets delivered to the engine. This causes the engine to rev up and surge.

  • Car does not start

One of the possible reasons why you cannot start your engine is because of fuel pump malfunction. Unfortunately, when a car doesn’t start, most vehicle owners do not think about the fuel pump as the culprit. Most will look at a dead battery, a defective starter, or problems with the alternator. These can also lead to a car not starting. However, one should never exclude the possibility of a defective fuel pump.

You can try to check the fuse for the fuel pump if it is already blown. If it is, then you can replace the blown fuse with a new one. You can also check the fuel pressure in the car’s fuel line.

Learning about the different signs of a bad fuel pump can help you determine the next action to take. Depending on the extent of the damage, you can either have the pump fixed or replace it with a new one.


  1. Signs a Fuel Pump Is Failing – It Still Runs
  2. Symptoms of a Bad or Failing Fuel Pump – Your Mechanic
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