Symptoms of A Faulty Fuel Pump

Fuel pump problem is not something we experience often.

Some people might not have to repair their fuel pump all through the years of using a vehicle while others might have to fix it after driving over 100,000 miles.

The fuel pump works with other components to deliver fuel from the tank to the engine to help it work.

Since most components of a car are linked together or interconnected, you might sometimes notice a fuel pump issue from the malfunctioning of other components of the car and not the fuel pump itself.

All vehicles come with a fuel pump, which could be electrical or mechanical, and if it becomes faulty, certain symptoms will be noticeable in your vehicle.

The fuel pump has the sole responsibility of supplying fuel to the engine and any issue with it will alter the performance of your car.

What is a Fuel Pump and How Does it Work?

The fuel pump is a component of an automobile that transfers fuel from its tank to the engine through the fuel filter and fuel rail.

The fuel pump can be controlled either mechanically or electrically, which means that fuel pumps are of two types – mechanical and electrical.

The fuel pump ensures steady delivery of fuel to the carburetor or injector of the engine making it an important component in the internal combustion process.

The fuel pump delivers the appropriate quantity of fuel and at the right time to the cylinder based on speed and load requirements.

When the car key is inserted and turned on, the vehicle makes some humming sounds. This indicates that the fuel pump has been activated and is being pressurized. At this moment, the pump is sending fuel to the engine.

The fuel is transferred from the tank through a pipe and when it gets to the engine, it mixes with air and combusts to create energy.

Knowing and understanding the roles of the fuel pump will help you to easily notice when there is a problem with it.

Here’s a basic process of how both electrical and mechanical fuel pumps work.

  1. Fuel is drawn from the fuel tank to the engine through a pipe. For an electric fuel pump, a piston moves the fuel from the tank through a fuel line and to the engine. For a mechanical fuel pump, the pump responds to camshaft spins and fuel gets to the pipe through suction.
  2. In some engines, the fuel line is linked directly to the cylinder. Fuel then travels to the cylinder through this line.
  3. After the fuel has been sent to the cylinder, the air is then injected inside it from the intake valves to form a mixture of air and fuel which is necessary for combustion. For some engines, air does not mix with fuel until they get to the cylinder while in carbureted engines, air mixes with fuel in the carburetor before it gets to the cylinder.
  4. The air and fuel mixture is compressed by the pistons in the cylinder. For gasoline engines, a spark plug creates a spark to ignite the air and fuel mixture which combusts to release energy.
  5. The energy that has been created will power the crankshaft and put your vehicle in motion. The fuel that traveled to the engine with the aid of the fuel pump has performed its function and the residue will be sent out as exhaust.

Since fuel pumps are of two types, the working principles will be discussed under each type.

Most modern vehicles are equipped with an electric fuel pump which is mounted in the fuel tank while others have mechanical fuel pumps.

Types of Fuel Pumps

As stated earlier, fuel pumps are of two types – mechanical and electrical fuel pumps, whatever the case may be, they must transfer fuel to the engine.

Mechanical fuel pump

Before electrical fuel injection was generally accepted, automobiles were built with mechanical fuel pumps.

A mechanical fuel pump is mounted beside the in-line cylinder or fitted in between two cylinder bores and it is operated through an eccentric on the engine camshaft.

Two common examples of mechanical pumps are; diaphragm and plunger-type pumps.

Mechanical fuel pumps are operated through the motion of the engine and they have few working parts which make them reliable and easy to diagnose and fix a problem.

The working principle of a mechanical pump is quite simple. The pump moves through a camshaft or a special shaft that is moved by the crankshaft. As the shaft rotates, the cam is moved under the pivoted lever and the lever is raised at one end.

The other end of the lever is loosely connected to a rubber diaphragm which makes up the bottom of a chamber in the pump. This part moves downward and pulls the diaphragm along. As the lever pulls the diaphragm down, a suction is created. This suction takes fuel into the fuel pump through a one-way valve. As the other rotating cam keeps rotating, the pressure on the lever is taken off, the return spring moves the lever back and tension is released on the diaphragm.

The loosely connected lever does not push the diaphragm up instead the return spring pushes against it. The diaphragm can only be pushed upward by expelling fuel from the engine. The fuel cannot return through the previous one-way valve, so it passes through another valve that leads to the carburetor. The carburetor allows only the quantity of fuel it needs through the needle valve in the float chamber and as the carburetor is full and remains closed, no fuel escapes from the fuel pump.

The diaphragm goes down while the lever idles up and down. When the carburetor opens up for more fuel, the return spring forces the diaphragm up and brings it to contact with the lever which pushes it down to refill the fuel pump chamber.

Electric fuel pump

Modern vehicles make use of electric pumps, which are kept in the fuel tank to generate high pressure in the fuel lines and channel fuel into the engine.

An electric pump has a similar valve and diaphragm arrangement as the mechanical pump but an electromagnetic switch (solenoid) replaces the camshaft which helps in pulling the diaphragm. An iron rod in the chamber pushes the diaphragm down to draw petrol into the chamber.

Once the ignition key is turned on by the user, the powertrain control module (PCM) puts on the relay that powers the fuel pump. The fuel pump’s electric motor rotates for some time to increase the fuel system pressure. Fuel is then introduced into the fuel pump by a suction valve. Subsequently, the fuel leaves through the check valve into the engine. The electric pumps are placed inside the fuel tank and the electromagnetic motors in the tank force fuel into the engine at high pressure.

A filter is present to filter off the dust, rust, and other debris. It also prevents them from blocking the injectors or entering the engine. Fuel then moves into the engine’s supply rails and is fed into various injectors.

The electric fuel pump keeps working as long as the engine has been turned on and can work at a steady or variable speed depending on the speed and load of the engine.

Electric pumps are made up of several moving parts and are linked to the electronic control system of the vehicle. Due to their complexity, they are more prone to failure than mechanical pumps.

Examples of electric pumps include inline, rotary vane, in-tank, and generator electric pumps.

Importance of a Fuel Pump

The fuel pump acts as the heart of the fuel system because it pumps fuel to all the necessary places. The fuel system can be described as the vascular system of your vehicle where the fuel pump serves as the heart, the lines act as the veins and the filter acts as the kidney. Failure of any of these components will affect the proper functioning of your vehicle.

The fuel pump is one of the most important components and plays a major role in the performance of the engine. It draws fuel from the fuel tank and moves it to the engine through the fuel line. It also helps the engine to maintain a particular fuel system pressure.

The fuel transferred is usually injected into the intake manifold or directly into the combustion chamber.

The fuel pump does not only push fuel into the engine, it also distributes fuel to the carburetor under low and higher pressure to the fuel injection system. It exerts adequate pressure which enables injectors to send the appropriate quantity of fuel to the engine.

The fuel pump serves as a mechanism that sends fuel to the injectors which transfer it to the internal combustion engine.

Symptoms of A Faulty Fuel Pump

Common Symptoms of a Faulty Fuel Pump

If your fuel pump is bad or failing, your car will exhibit some of the following symptoms.

Engine stalling

If your fuel pump is faulty, your engine can stall unexpectedly. Engine stalling sometimes is not a clutch problem like you might suspect, it could be that the fuel pump isn’t providing enough fuel to the engine for its operation.

This can be quite frustrating if it happens while idling in the traffic. Stalling usually comes with high engine temperature which is indicated in the car’s thermometer gauge.

Since the pump is bad, it does not send enough fuel to the engine which causes the engine to strain and overheat. Sometimes, the engine may stall to prevent overheating.

Dead engine

If the fuel pump is bad, cranking the engine might take longer or won’t even be possible.

A faulty fuel pump will make it difficult to start the engine due to a lack of pressure. Fuel pumps begin to work once the ignition is turned on, if your engine takes more cranks to start, it means that it isn’t receiving enough fuel which indicates that the fuel pump is faulty.

Sometimes, it might get more serious that the engine does not start at all. Since the engine is lacking fuel, it might crank when the ignition is turned on but the car will not start.

Hesitant acceleration

Delayed acceleration can be an indicator that your fuel pump is bad.

When the fuel pump fails to produce the required volume of pressure, the vehicle will be unable to accelerate. Accelerating needs more fuel and this gives the fuel pump extra work in pumping more fuel.

If the pump is bad, it won’t be able to meet this extra demand. The inability of your car to accelerate is enough indication that you need to inspect your car pump.

Bad fuel economy

A bad fuel pump will cause excess fuel to get into the engine system. The excess fuel doesn’t get used up or stored, rather it burns off unnecessarily.

If you notice an increased fuel consumption and you have to refuel your car more often, it is important to assess your fuel pump to confirm if there is a problem with it.

Engine sputtering

A sputtering engine will make an unusually loud sound. This shows that the engine has not been able to achieve complete combustion.

The engine might not achieve full combustion because the fuel pump is bad and not propelling the required quantity of fuel to the engine.

If you’re driving your vehicle at a high speed and it sputters, one reason for this could be a fuel pump issue.

Engine surging

If your engine starts and speeds up smoothly but surges or misfires along the line after minutes of constant speed, this means that more fuel than required is being injected into the engine and fuel pressure is rapidly increasing, which is a symptom of a faulty fuel pump.

Unsteady fuel flow will cause an engine surge because it has skipped some power strokes. The car will want to accelerate and slow down at intervals which is very dangerous if you are on the road.

Check engine light illuminates

When the check engine light beams, it could be a problem with one or more components in the engine.

A bad fuel pump can also cause the check engine light to come on.

Power reduction

Once the engine is not getting the right amount of fuel for its operation, its performance and power will reduce.

You will experience this power reduction when your car cannot maintain speed on the road or find it difficult to climb a hill. Also, when you try to accelerate and your car loses power, there might be a problem with your fuel pump.

All these activities require more fuel to yield a good performance and if your fuel pump is bad, it cannot meet up with this demand.

If the fuel pump is faulty in this situation, it can’t maintain a steady flow of fuel which will lead to loss of power.

Noise from the fuel tank

If you notice some noise from the fuel tank, it could mean that your fuel pump is failing. When this happens, the fuel pump generates high friction, overheats, and gets noisier.

Normally, the fuel pump makes a barely noticeable sound but when this sound gets louder than usual, it could be indicating there’s a problem.

Causes of Early Fuel Pump Failure

There are several reasons why your fuel pump might fail. Here are some causes of early fuel pump failure.

Contaminated fuel

Fuel can be contaminated with sludge, debris, rust, or moisture. Any form of a contaminant in the fuel tank can cause problems for the fuel pump because it will get stuck somewhere.

Clogged filters

Certain contaminants will clog other components of the fuel system like the filters or strainers which will restrain the free flow of fuel from the tank to the engine.

The strainer/filter is positioned inside the fuel tank and it prevents debris from getting into the fuel pump, if they are blocked, the pump will not be able to receive an adequate amount of fuel as there is an obstruction in the strainer or filter.

The pressure in the fuel line will be low as a result of this.

Electrical faults

Problems with some electrical components can also lead to fuel pump issues.

Loose or rusted connectors and melted wirings are some major electrical problems that can cause fuel pump failure. This type of issue can be diagnosed by testing with a high digital volt/ohm meter.

Low fuel

Running your car regularly on a low/reserved fuel level can damage your fuel pump.

An insufficient quantity of fuel in the engine will cause the engine to overheat which will, in turn, cause the fuel pump and other internal components to wear out.

Worn-out pump

A worn-out fuel pump will cause issues to your vehicle. Fuel pumps wear out with time although this might take a while. You can drive your vehicle for over 100,000 miles before you start bothering about fuel pump issues.

How Long Can the Fuel Pump last?

Fuel pumps do not require regular maintenance because they can last for a long time. Unlike some other components in the engine, the fuel pump can last for over 100,000 miles, in some cases, it can last for up to 200,000.

If you practice good driving habits and take care of your fuel pump and other components by ensuring you get quality fuel from a reliable gas station, you don’t run out of fuel often, top-up fuel when it gets low, and inspect and replace your filter more often, your pump will last for a longer time.

Fuel pumps are durable and reliable, they are not a part of a vehicle’s regular maintenance schedule and are replaced only when they go bad which happens after a long time of driving your vehicle.

The type of pump, driving environment, and level of application and maintenance all determine the lifespan of your fuel pump.

How to Maintain your Fuel Pump

Most fuel pump issues are always linked to problems from other components like a clogged filter and strainer, contaminated fuel, or damaged fuel lines.

Here are a few maintenance tips that will improve the longevity of your fuel pump.

Regular fuel system checks and cleanup

It is important to inspect your fuel system regularly and clean it up. Ensure the tank, filters, strainers, fuel lines, and pumps are in order.

This will help you to detect a problem with any of these components on time before it gets complicated.

The fuel tank should be at least a quarter way full

Low fuel will require the fuel pump to do more work in sending the appropriate quantity of fuel to the engine, and this will weaken the fuel pump.

Also, fuel serves as a coolant to the fuel pump inside the tank, so if you are always running your car with an almost empty tank, you are staking the lifespan of your fuel pump because it will constantly overheat.

Keep to fuel filter change interval

You must endeavor to change your filter and other components that might cause problems to the fuel pump following the manufacturer’s recommended change interval.

It is also important to use OEM component specifications for your vehicle when carrying out the changes.

Fuel separation

Fuel jell is one of the common causes of injectors and fuel pump issues.

If you won’t drive your car for one or more weeks with fuel in the tank, it is important to add an anti-ethanol agent so that the fuel will not jell.

Gasoline on its own might not jell, but other elements that find their way into the fuel tank might cause this to happen.

How to Test and Diagnose Fuel Pump Problems

Working on your engine can be messy and a bit dangerous. For safety, you need tools like safety glasses, gloves, and mechanic coveralls while working on the engine.

To test the fuel pump, you will need tools like:

  • Socket set.
  • A multimeter.
  • Hose clamp pliers.
  • Screwdriver set.
  • Siphon pump.
  • Microfiber towels.
  • Air compressor.

Certain symptoms will enable you to know when it’s time to test and diagnose fuel pump problems.

As explained earlier, some of those symptoms include; reduction in power, engine surging and sputtering, bad fuel economy, etc. Before running the fuel pump test, the first thing to do is to verify if it is a fuel pump problem by inspecting, then you do the following.

  1. Ensure the battery is fully charged: The battery supplies power to the fuel pump. So, before the testing, ensure the battery is fully charged. A dead battery will restrict you from carrying out the test effectively, but when there’s power in the battery, you can test and ascertain if the problem is from the fuel pump, its connections, or peripherals.
  2. Use a test light to inspect the fuse: Firstly, ensure the test light is working well, then place the lead end on the negative battery terminal and the test light tip on the positive terminal. When this is done, open the fuse box and test each fuse one after the other to enable you to know if you have a blown fuse or not. A fuel pump could be sucking too much electrical power because of a bad fuse, so it is important to test and replace a bad fuse.
  3. Check the fuel pump pressure: Locate the service cap on your rail, close to the injectors. Remove the cap and you will see a Schrader valve and connect a fuel pressure gauge on this as outlined in the repair manual. Turn on the ignition key and the reading will appear on the gauge. The pressure reading should be between 45 psi and 60 psi.
  4. Locate the fuel pump: If the pressure gauge reads that there is no pressure, it indicates there is a problem with the fuel pump. The fuel pump is usually found in the fuel tank in most modern vehicles and to access this, you need to take off your back seat cushion to get to the fuel tank. Check if you have a serviceable fuel filter. If you have not replaced your filter in a while as recommended, you might want to do that first.

To test the fuel pump, have someone turn on the car, then place your ear close to the tank to know if it is buzzing, if this happens, it means that the fuel pump has turned on too. Place a digital multimeter with an amp clamp over the positive wire that is going to the fuel pump, using a voltmeter to set the amperage. Start the car and record the amperage reading on the meter. This procedure enables you to know how much the pump is working and the amperage it is using. If the reading does not tally with the manufacturer’s recommendations, then it’s time to replace the fuel pump.

  1. Test the fuel pump for power and ground: After locating the fuel pump, you will notice a connector. This connector sends power to the fuel pump and you need to twitch it first before disconnecting to ensure it wasn’t loosely connected. The connector comprises two thick wires and two thin wires. The thick wires are for power and ground while the thin wires are the level sensors that send power to the gauge cluster.

Create a complete circuit by connecting one jumper wire to the power wire and another to the ground wire and connecting both ends of the jumper wires to the test light. Have someone turn on the ignition key while you hold on to this connection. If the test light illuminates, it means you have good power and ground going to the fuel pump but a bad fuel pump that is not pressurizing the fuel needs to be changed.

  1. Check for lost power or ground: Connect the lead end of the test light to the ground and the tip to a power wire to ascertain if there is or if there is no power going into the fuel pump. A perfect ground could be a bolt in the car’s door. After achieving this, have someone turn the key on and off. The test light will illuminate if there is power. To assess the ground, connect the lead end of the test light to the positive terminal of the battery and then the test light tip to the ground wire. If the test light comes on when the ignition key is turned on, then you have a good ground.

Fuel Pump Replacement Cost

Depending on your car model and make, a new fuel pump can cost between $100 to $1200 or even more.

The cost of labor also varies based on the make and model of your vehicle. Labor can cost anything between $120 to $240. The total cost of replacement will be between $270 to $1500.

For cheaper services, you can have your car pump replaced at a good independent auto shop instead of a dealership because they tend to be more expensive. However, if you are to do this, ensure your mechanic uses OEM specifications to avoid future complications.

Frequently Asked Questions

What happens if the fuel pump goes out while driving?

The car engine cannot function without fuel and the fuel pump must send the required amount of fuel to the engine. If the fuel pump goes out while driving, your car will stop moving. A failing fuel pump reduces car performance. When the cylinders are not getting fuel anymore, the pistons stop firing, your car stops and will not move until this is fixed.

Will a bad fuel pump throw a code?

Just like many other car defaults, a bad fuel pump will trigger the P0087 trouble code. A sensor on the fuel rail monitors fuel pressure and checks if the engine needs less or more fuel. Symptoms will appear if the fuel pump is bad and will cause the Engine Control Module (ECM) to throw the P0087 trouble code.

Can you drive with a bad fuel pump?

Absolutely no! If the fuel pump is bad, it can no longer supply the cylinders with adequate fuel and pressure. Your car will even struggle to start because the cylinder is not getting enough fuel, if it eventually comes on, it will stop moving unexpectedly at any point.

Can the fuel pump be cleaned without removal?

Yes! You can clean the fuel pump without removing it, although this cannot be done easily in some vehicles. If you have an electrical pump, you can clean it up by putting a fuel system cleaner into an almost empty fuel tank, pumping in new fuel which will mix with the cleaner, put on your engine and let it idle for some minutes. The cleaner will run through the fuel filter, pump, and the engine and will break down unwanted deposits in the fuel system. For a manual pump which is usually found on the engine and not in the fuel tank, you can open it and clear off debris in the internal filter.

What can I do if my fuel pump is failing?

If you notice your fuel pump is failing as a result of any of the symptoms discussed earlier, all you need to do is to take it to an auto repair shop for a replacement. If you can do this on your own, what you have to do is to buy the recommended replacement, follow the manufacturer’s repair manual and get it done. You cannot drive your car with a bad fuel pump, so it is important to get it fixed as soon as possible.

What will cause a new fuel pump to go bad?

A new fuel pump can go bad due to electrical faults, improper installment, or lack of pressure in the pump. Even if the pump is working, if there is no pressure, the engine’s performance will be hindered. Also, if you use a poor-quality pump that is not recommended for your vehicle model/make, the pump can go bad just after installation.

Can a fuel pump fail suddenly?

Fuel pump problems are usually unpredictable and sudden. Although, if you pay close attention to your vehicle before driving it out, you might notice some prospective signs of pump failure. If you don’t do this, your fuel pump can fail at any time and will hinder the movement of your vehicle.

How long can I drive with a bad fuel pump?

It is very risky to drive with a bad fuel pump because your car can stop working anywhere even in the middle of the highway or while idling in traffic. This happens because the pump is no longer supplying enough fuel and constant pressure which is needed to move the vehicle. You should not drive with a bad fuel pump and if you notice the condition of the fuel pump late, you should immediately take your car to a mechanic.

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