Signs Of A Failing Fuel Pump | Explained

It’s not always easy to detect a failing fuel pump if you don’t know the signs. Most units are located inside the fuel tank from where they pump fuel and send it to the engine. There’s usually no way to see it without removing the rear seat or trunk floor.

To determine whether the problems you’re experiencing are due to a bad fuel pump, you’ll need to listen carefully and pay attention to the signs. In this article, we’ll highlight some of the most common fuel pump symptoms that you should watch out for.

This will help you determine whether the problem lies with the pump or other related parts such as the fuel line, fuel filter, or fuel injectors. But first, let’s distinguish between the two most common types of pumps available in most cars.

Types of Fuel Pumps

·       Mechanical fuel pump

Mechanical fuel pumps are driven by the motion of the engine. They contain a diaphragm or plunger that expands and contracts to create low pressure. This forces the fuel out of the tank and into the engine.

Older models send fuel to the carburetor where it mixes with air before sending it to the engine. Overall, these types are reliable and simple. However, due to their position inside the engine bay, they tend to cause problems with the fuel line.

The fuel line is susceptible to airlock if there’s excess heat from the engine, exhaust system, or the external environment. An airlock can cause several issues, including stalling, loss of power, and a no-start condition.

·       Electric fuel pump

All modern vehicles today feature an electric fuel pump that’s located inside the fuel tank. It’s usually submerged in gasoline and is powered by the car’s electrical system. It has a diaphragm that is actuated by a solenoid. This allows it to draw fuel to the pump.

The pump sends the fuel down a fuel line and into the engine. Electric units eliminate vapor lock by pressurizing the gas from inside the tank. They are simple and reliable. However, they are not without fault.

Some of them can be very hard to replace. Others are sensitive to rust and sediments and most do not come with effective filters. While it’s not easy for them to overheat, they can heat up when the tank is low on fuel.

9 Signs of a Failing Fuel Pump

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Most of the signs that you’ll notice when your fuel pump fails relate to the performance of the car. Fuel is crucial to the engine’s operation and without it, the motor will struggle to provide the power you need.

Here are the most common signs of a bad fuel pump.

1.    Car Doesn’t Start

While a no-start condition can be caused by a result of bad spark plugs and a myriad of other issues, one fairly common cause could be the fuel pump. The engine will crank but since the pump can’t deliver fuel to the engine, the car will not start.

Ideally, when you turn the key, the electrical circuit between the battery and the starter motor closes. The starter motor allows the engine to reach a certain RPM for it to initiate operation under its own power.

The starter motor’s job is to turn electrical energy into mechanical energy. One thing that you’ll notice is that if you continue to start the car and it fails, the battery eventually drains. This will put excess stress on the system and cause expensive repairs.

2.    Loss of Power

The car might lose power when driving uphill or when towing a heavy load. Such situations typically demand more power. The fuel pump is responsible for delivering more fuel to meet the demand.

If it fails, the car will start to drag. The pump will not be able to pressurize the fuel, preventing it from reaching the engine. The same thing happens when accelerating or when driving the car at its limit.

3.    Engine Surges

If the pump continues to fail to deliver fuel to the engine, the latter will sputter and surge. This happens due to a lack of steady flow of fuel, hence, affecting engine performance. The car will jerk as it struggles to keep moving.

The same thing can happen if the fuel pump is intermittently sending too much fuel to the engine. The engine will pick up and then drop its speed as you drive. This is a sign that it’s receiving more air than fuel in its cycle.

4.    Stalling

Another common sign of a failing fuel pump is a car that stalls at high temperatures. When the engine does not receive enough fuel, it is forced to work a lot harder to stay operational. This can cause it to overheat.

You’ll see the temperature gauge on your instrument cluster rise followed by a stalling engine. Pay closer attention to your fuel pump when this happens. Operating the engine at extremely high temperatures can lead to expensive damages.

5.    Whining Noises

As mentioned earlier, modern vehicles have electric fuel pumps that are located inside the gas tank. One of the most common signs of a failing fuel pump is a loud whining noise coming from underneath the trunk floor or rear seat.

This is usually an indication that something is wrong. Many units tend to hum silently when operating normally. They produce an excessively loud noise when they go bad. It could also be a sign that the car has run out of gas or that the fuel is contaminated.

To confirm the noises, put your ear close to where the fuel tank is located in your car. Have a friend or partner turn the key to the on position inside the ignition. You’ll hear a sound indicating that the pump is now active. Have the other person crank the engine to hear if there are any unusual noises coming from the pump.

6.    Fuel Inefficiency

A bad fuel pump will definitely affect how your car consumes fuel. In many cases, you’ll find yourself taking more trips to the gas station to fill up your tank. A drop in fuel economy is mostly caused by a rich condition – where the engine receives more fuel than is necessary.

Rarely do pumps cause rich conditions. The most probable culprit is a failing fuel pressure sensor or a bad pressure regulator that causes fuel to flow inconsistently. The pump operates at a higher psi than required, causing the engine to consume too much fuel.

7.    Rough Idle

An engine needs about 0.5 gallons of fuel every hour when idling. This varies from engine to engine depending on the type. Smaller cars will typically burn less while SUVs and large sedans will burn more.

If the fuel pump becomes defective or clogs, it will not send enough fuel to the engine. This will result in rough idles and poor acceleration. You may also notice sputtering and stalling in serious situations.

8.    Check Engine Light

There are about 1,400 reasons why a check engine light would flash on your car. A bad fuel pump or bad fuel pressure sensor is one of them. It will typically generate a P0087 diagnostic trouble code. A failing fuel pump will affect how the engine in your vehicle performs.

The work of the ECU is to monitor such discrepancies and notify you through the check engine light. It could also have been triggered by the resulting engine misfires or emission issues that arise from a faulty fuel pump.

9.    Engine misfires

Misfires occur when a cylinder(s) does not produce the power needed to keep the car running. One of the main causes behind it is if there is a problem in fuel delivery due to a faulty fuel pump.

Some of the signs of an engine misfire include a car that is shaking, slower acceleration, and engine hesitation. The engine may vibrate more than usual when idle and run unevenly. While the cause may not be that obvious, the fuel pump is a good place to check when diagnosing the problem.

What happens when the fuel pump goes out while driving?

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A failing fuel pump will cause the car to behave in some of the ways described above. It will affect fuel delivery to the engine, meaning that there won’t be enough to mix with the air. This will affect combustion and how the engine produces power for motion.

Some of the immediate signs include a loss of power and poor acceleration. The engine may surge and sputter as it showcases signs of a misfire. If you continue driving, you may also hear whining noises in the back seat. Eventually, the car will stall due to a lack of fuel inside the engine.

It’s best to stop the car immediately you notice signs of a bad or failing fuel pump. Call a tow truck or a mobile mechanic that you trust and have them take a look at the vehicle before you proceed. Otherwise, you’ll be going nowhere fast.

How long can you drive with a bad fuel pump?

Fuel pumps are designed to last up to 100,000 miles. Many have lasted longer than that, crossing the 200,000-mile mark without needing repairs or replacement. When your pump goes bad, you may not be able to drive for more than 30 minutes.

A fuel pump that stops working suddenly will not deliver the fuel needed to keep the car running. The engine will get hot before it stops working. You will not be able to start the car at all. Once your car covers more than 100,000 miles, watch out for the signs and consider replacing your failing fuel pump.

How expensive is it to replace a fuel pump?

According to KBB, the replacement cost of a fuel pump ranges between $220 and $1,062 depending on the type of vehicle you drive and its age. A certified mechanic will charge you anywhere between $124 and $260 for labor. Parts cost as little as $95 and can run up to $854.

These estimates do not include additional fees and taxes. As a rule of thumb, expect to spend anywhere between $400 and $600 when getting your fuel pump replaced by a mechanic.

How many hours does it take to replace a fuel pump?

It takes between 2 and 3 hours to replace a fuel pump. The average for most cars is 2 hours. The process involves draining the gas tank, removing it from its location, washing out any debris, and replacing the fuel pump.

In some cars, the fuel pump can be accessed without removing the gas tank. One thing, however, remains the same – all cars made after the mid-1990s have fuel pumps located inside the gas tank. You can check out this detailed guide on what it takes to work on the fuel tank.

Maintenance tips to help improve the performance of your fuel pump

·       Always have the gas tank at least a quarter full

A gas tank that runs empty often can cause the pump to overheat, reducing its lifespan. Also, an empty gas tank usually causes the engine to draw in air. This can cause stalling and prevent the car from starting.

Having a tank that is at least a quarter full helps to prevent sediment buildup in the tank. The warning light will typically illuminate when the tank is about 15% full. Don’t cover more than 30 miles without refilling the tank.

·       Do regular fuel system checks and maintenance

Inspect the fuel filter regularly and replace it when it gets clogged by sediments and debris. Consider using a fuel system cleaner or fuel injector cleaner to eliminate dirt and carbon buildup in the fuel system.

If you have a car that has been sitting for a very long time with gas in it, consider cleaning the tank before adding any more fuel. Gasoline has a shelf life of about 6 months. Diesel can last about a year before it starts to deteriorate. Cleaning the tank prevents causing damage to the pump.

Final Note

A failing fuel pump isn’t the easiest job if you have no idea what the signs are. It requires some skill and extra time on your hands. As such, it’s often best left to a professional when you notice any signs of failure. Consult your mechanic and have them replace it for you. A new pump should serve you for another 100,000 miles before needing another replacement.