The Ultimate Guide
The automotive fuel pump. Ask any car owner about this vehicle component, and chances are they won’t know much about it. Maybe, only that it has something to do with pumping fuel. Well, it does, but the truth is many people don’t know a lot about the fuel pump- how it operates, how to tell when it fails or even what to do to fix a failed one.
If you fall into this group, worry no more. We put together this fuel pump guide to provide you with an ultimate resource for fuel pumps. It contains information’s about all aspects of the device, from what it is, where to find it in a vehicle, to the troubleshooting methods. The measures to take, too, when the pump malfunctions.
Reading it to the end will equip you with the knowledge to care for this crucial component. Or, you can click on the chapter that contains the information that you are looking for. Each chapter is a comprehensive guide for the particular topic.
What Is A Fuel Pump
A vehicle comes with many different components, all serving specific purposes. One of them, and among the most crucial, is the fuel pump. You will find this device in virtually car or truck, both, classic and modern.
What function does the fuel pump fulfill that makes it so common in motor vehicles? This chapter answers that question and many more. Read on, and understand why your car needs a fuel pump.
Before we delve into the work of a fuel pump, let’s first understand what this component is. Also, its location in an automobile.
What is a fuel pump?
In basic terms, it is the device that pumps fuel to the engine. A fuel pump is easily recognizable by its distinct look as well location.
In the older motor vehicles that used carburetors, the fuel pump mounts on the engine block. Modern automobiles have the pump installed either in the fuel tank or outside, along the fuel line.
As we have seen, fuel pumps crucial vehicle components. Why? Let’s see.
Fuel Pump Function
Fuel pumps help to supply the engine with the required amount of fuel. At the right pressure, too. That way, a vehicle runs smoothly in different driving conditions, fuel requirements, and other demands.
Without a fuel pump, it would be difficult to create the required pressure to supply fuel to the injection engine. The fuel would sit in the fuel tank serving no useful purpose.
To understand the value of a fuel pump, you only need to drive a vehicle whose pump is faulty. You would find drivability to be greatly affected and the engine performance too low.
Next, about the different fuel pumps that vehicles, both old and modern, use.
Types of Fuel Pumps
Fuel pumps come in two types: mechanical and electrical. Mechanical pumps are driven by the vehicle’s engine while electric fuel pumps rely on power supplied by the battery or alternator. For clarity, let us look at the two fuel pump types in detail.
Mechanical Fuel Pump
This type of fuel pump is usually found in the older vehicles that used carbureted engines. The pump is fast becoming obsolete, though, as manufacturers phase out carburetors in favor or fuel injection systems. That’s why only a few automobiles use these pumps today.
Mechanical fuel pumps mainly rely on suction to move fuel out of the fuel tank and convey it to the engine. For that reason, they’re said to be “puller” pumps. These pumps also depend on the motion of the vehicle’s engine to work.
Because mechanical pumps create immense suction but low fuel pressure, they’re usually located near the carburetor or engine, and far from the fuel tank. That way, they can draw fuel and still manage enough pressure to send it to the carburetor.
Electrical Fuel Pump
This is the standard fuel pump in the vehicles that use direct injection engines. That means virtually every vehicle today uses an electrical fuel pump send fuel to the engine.
In contrast to the mechanical type, most electric fuel pumps use a push action to force fuel through the fuel lines. As a result, they do not need to be near the engine to deliver fuel efficiently. It’s one of the reasons why they mount inside the fuel tank or fuel line.
Electric fuel pumps can either be in-tank or in-line.
- In-tank electric fuel pumps, as the name suggests, are placed inside the fuel tanks. They’re the most common for the many advantages the positioning offers. Because of the immersion in fuel, these pumps don’t run hot as the fuel continually cools them. The possibility of these pumps causing a fire is also minimized due to the absence of air in the tank. Also, the possibility of the pump sucking in air greatly reduces.
- In-line electric fuel pumps are located outside the fuel tank but not far from it. These pumps are not common since they don’t come with many benefits. Usually, car owners install them when the in-tank pump has failed, and there’s not enough time to replace it. Mounting a temporary pump on the fuel line restores the performance of the car until that time when you change the damaged one. As you can openly see, one advantage of these “outside” fuel pumps is that they’re easy to fix.
How Does a Fuel Pump Work?
That depends on the type of pump. Although the basic fuel pump working principle remains simple, some pumps are more complex than the others. A good example is an electric fuel pump. These pumps have more components than the mechanical type, and their operation is also somewhat complicated.
In its simplest form, a fuel pump working mechanism involves only a few parts; a diaphragm that moves up to allow fuel into a chamber and down to push the fuel out. Another design, and the most popular one, features a DC motor that spins to “push” fuel through the fuel lines and into the engine.
To better understand the operation of fuel pumps, let’s have a look at the working of each type in detail.
Mechanical fuel pump: how it works
An eccentric on the camshaft is what drives a mechanical pump. These pumps primarily consist of a pivoted lever, a rubber diaphragm, a return spring, inlet and outlet valves, and the housing. This is what happens.
- As the camshaft rotates, the eccentric moves the pivoted lever up. This causes the other end of the lever to move down
- A rod connected to the lever pushes the diaphragm down when the lever is actuated by the eccentric
- This causes the diaphragm to move downwards and create a low-pressure space above it. The action also closes the fuel outlet and opens the inlet
- The drop in pressure causes fuel to enter the pump’s chamber through the inlet valve
- Meanwhile, a return spring pulls the diaphragm up, closing the inlet and opening the outlet valves
- The resulting pressure pushes fuel out through the pump’s outlet and to the carburetor
- The process repeats, moving the diaphragm up and down and sending fuel to the engine as needed
This video details the working principle of a mechanical fuel pump:
Electric fuel pump: how it works
Electric fuel pumps are a little bit more sophisticated than the mechanical type. They also come with more parts. Most these pumps come as part of a fuel pump module, that’s, an assembly consisting of sensors, filter, electrical connections, and other components.
All electrical fuel pumps don’t work the same way. Some use a mechanism that’s similar to that of mechanical fuel pumps, while others use a spinning motor to pump fuel. These are the only two methods of operation for the electric type of fuel pumps.
Let’s start by looking at how an electric diaphragm-and-chamber fuel pump works. This is what happens.
- A solenoid, upon receiving current, becomes magnetized and attracts an iron rod
- The iron rod is connected to the diaphragm. Its moving pulls the diaphragm down
- The resulting space causes a pressure drop and fuel moves in through the inlet valve
- The rod reaches a point where it parts a set of electrical contacts and breaks the circuit
- The solenoid loses magnetism and stops attracting the iron rod
- A return spring pulls the diaphragm up, an action that pushes the drawn fuel up the fuel line
- The relaxing diaphragm pulls at the iron rod, the contacts close again, magnetizing the solenoid and causing the pumping action to repeat
This is how the spinning motor electric fuel pump works.
- When you turn on the ignition key, a relay sends a voltage to the pump
- This activates the motor that starts to spin immediately
- Spinning works a mechanism that moves fuel up the pump
- After a few seconds of spinning to build up pressure, the pump releases the fuel into the fuel line
- The process continues, and the pump continually pushes fuel toward the engine at the right pressure and amount. Sensors attached to the pump assembly allow that to happen
This video explains the above working of an electric fuel pump :
As we have seen, electrical fuel pumps are used to dispense fuel to the injection type of engines. These engines require fuel to be delivered at high pressures, usually about 45 and 65 pounds. Only electrical fuel pumps can manage that.
The mechanical types usually achieve less than 10 pounds of pressure- enough for a carburetors requirements but much less than what a fuel injection engine would need. That’s why the mechanical pump is only suitable for carburetor engines and the reason they’re not widely in use today.
A properly working fuel pump means a vehicle that drives smoothly and at a consistent speed. But sometimes the pump fails due to various reasons. How can you tell when this happens? Read about that on the next chapter of this guide.
Symptoms of Bad Fuel Pump
Just like any other other component, a fuel pump will eventually wear down. The time it takes to do so varies from one pump to another. One fuel type will outlast another, and a brand will last for a longer time than the other. Most of the time, a fuel pump’s lifespan depends on how well you care for it, how effectively you protect it from damage.
When a fuel pump breaks down for whatever reason, it stops serving its purpose. If the damage is only slight, the pump will weaken and send inadequate amounts of fuel to the engine- and at low pressure. The faulty pump will often produce detectable signs. A fuel-starved engine, too.
So, What are the Symptoms of a Bad Fuel Pump?
Engine Struggling to Start
A fuel pump runs whenever the engine is on. This causes it to wear down over time and weaken. Eventually, the pressure it produces to pump fuel drops. The engine then doesn’t receive adequate fuel and at the right pressure. As a result, you experience difficulty getting it to start.
If your car or truck requires several cranks to start, its one of the weak fuel pump symptoms. Other failing components could be the reason for the multiple starts, of course. So you may need to rule out those first.
Decreasing Fuel Mileage
A fuel pump comes with a relief valve that regulates the amount of fuel it sends to the engine. If the valve fails to open as required, more than enough fuel goes to the engine. This causes the fuel tank to empty too fast.
If you find yourself filling the car with fuel more often than before, the fuel pump could be weak. You may need to check its relief valve, especially if you have used the car for long without changing the pump.
Engine Losing Power When Under Stress
Some driving situations require the engine to operate more powerfully. They include driving uphill or hauling loads that are too heavy. Because of the extra force needed, the engine has to burn more fuel.
If your fuel pump is failing, it may not cope with the demand for extra fuel. The pressure with which it pushes fuel to the engine may be too low, and the fuel amount inadequate. Your car then experiences loss of power and you feel it struggle to move along.
Accelerating from a stop situation requires a sudden increase in the amount of fuel reaching the engine. A weak fuel pump cannot keep up with this immediate demand. As a result, the car doesn’t accelerate as required.
If your car almost stalls when you want it to move forward fast, one of the most likely reasons is a fuel pump problem. Other vehicle components could also be the cause, so you may need to consider all the possible reasons.
Increased Temperatures Before Stalling
This is a common problem that can indicate fuel pump issues. It happens when the resistance at the pump’s motor becomes too high and causes overheating. The temperature gauge of your car then registers a heightened temperature level and the car stalls.
A word of caution, though. Other components can also cause these series of events. Therefore, it’s good if you check those too when you experience this issue. You may, for example, want to rule out an empty fuel tank.
This symptom results from a pump that fails suddenly while in operation. The engine receives air instead of fuel, and a few power strokes get interrupted. You feel a jerk or sputter of the engine, but that doesn’t last for long.
Engine sputters mostly happen when you’re cruising down a road at high speed. At first, these jerks are short lived. They become more frequent and longer as the fuel pump problems become more pronounced.
No Sound from the Fuel Pump
Typically, fuel pumps make whooshing sound or when they come alive. You may also hear a soft hum. If the pump remains silent when you’ve put on the ignition key, it could mean the pump is not working at all.
The problem could be a faulty relay, or it could be the pump itself. This symptom of a bad fuel pump is one of the most serious. It can mean a car that won’t start at all, and you may need to take prompt action.
Whine or Howl From the Fuel Tank
A fuel pump should produce a humming sound when you turn in the ignition key or when running. If this sound transforms into a whine or howl, it indicates an issue with the fuel transmission system.
The problem could be either insufficient fuel reaching the engine, or the fuel could be having contaminants. However, the culprit is often a bad fuel pump which then needs to be checked. The good thing is, this symptom is easy to pick.
These result from irregular increases of resistance in the motor of the fuel pump. When they occur, you feel the car move forward suddenly, like you’ve just depressed the gas pedal.
Surges that result from a faulty fuel pump often happen randomly without warning. Also, when you’re driving at a constant speed and not expecting any sudden change of car movement.
These symptoms of a bad fuel pump are easy to detect if you’re keen enough. Most of them involve audible signals and other things you can feel while driving. While different types of fuel pump malfunction differently, the signs of damage of weakening mostly manifest the same way.
It’s good to note that an electric fuel pump is more prone to damage than the mechanical type. Its working action is controlled by circuits and various parts which are likely to fail. Additionally, these pumps contain more components that should work right at all times.
A mechanical fuel pump, on the other hand, contains fewer parts. Apart from being easy to fix, the pump is less likely to fail. Nevertheless, you may want to pay close attention to any indicator that it has broken down.
But there are times when you cannot tell if a symptom truly indicates a faulty fuel pump. During such times, it’s essential that you carry out tests to confirm that. That’s what the next chapter covers: troubleshooting fuel pump problems.
Fuel Pump Troubleshooting/Diagnose
Knowing how to troubleshoot a fuel pump is a skill that anyone needs to possess. It helps you tell when the pump is doing well, when it’s faulty, and what part requires repair. And if the pump needs replacing, when and how to do so. This chapter covers those aspects in detail.
Fuel pump troubleshooting may not be an easy task. However, that should not stop or discourage you from wanting to find out the problem with your car. With only a few tools and equipment, you can test your fuel pump to ascertain if its faulty or not.
Before we look at how to check a fuel pump for wear or damage, let’s see what causes the signs of fuel pump failure. These are the causes of various pump fails.
Increased Pump Pressure- fuel pressure that’s too high usually indicates a faulty relief valve. The valve prevents pressure from building up to levels that are too high. If you notice the engine consuming too much fuel, the pump could be at fault
Low Pump Pressure- this can result from physical wear, ruptured diaphragm, leaking valves, or weak return spring. Low pressure decreases the amount of fuel that the pump delivers to the engine. The engine starves and fails to start. When in motion, a starved engine could cause power loss or even total stalling of the vehicle.
Leaking Fuel- in this case, there’s the possibility that the pump suffered physical damage. It could also be that the diaphragm has deteriorated and ruptured. Still, it could be a case of a gasket that has weakened.
Fuel Pump Noise- in a mechanical fuel pump, noise could be caused by a weak return spring or lever. Not only weakness but also if those parts happen to break down completely. Note that a pump will make the normal noise when operating and you may need to be keen when deciding if the one coming from the pump is abnormal.
Overheating- this happens when there’s a lot of resistance in the pump’s motor. While fuel adequately cools the immersed fuel pump, excessive heating is not healthy for the pump.
How to Test a Fuel Pump
The procedure usually involves testing for fuel pressure and volume. It’s worth noting that different fuel pump designs may require different testing methods.
Before starting the tests, ensure that you confirm these issues:
- That there enough fuel in the fuel tank. If there isn’t, your pump may not be the problem for the car not starting
- That noise comes from the pump itself. If you turn on the ignition key, you should hear no other sounds apart from the wish sound of the fuel pump
- Check the pump’s fuel filter. If it’s clogged, it could be affecting fuel uptake and, therefore, transmission
Carrying out the Actual Tests
- Fuel pump pressure Test:
High pressure causes increased fuel consumption or a rich fuel mixture, while low pressure can result in the engine losing power. That happens especially when trying to accelerate or when carrying heavy cargo. Testing a fuel pump enables you to catch issues before they get out hand. Also, you get to eliminate drivability problems.
Here is the procedure
- Get a fuel pressure gauge
- Attach the pressure gauge to the fuel pump. You may want to consult your car’s manual to locate the test port. That’s because the ports are differently positioned from one vehicle to another
- Have someone rev the engine while you check the pressure gauge
- Determine the pressure when the engine is idling
- The pressure should be in line with what’s indicated in the repair manual of your car
- If it isn’t, your fuel pump is faulty and you may need to change it. If the problem can be fixed, then you can have the pump repaired
Fuel Pump Replacement
When a fuel pump weakens, it sends insufficient fuel to the carburetor or fuel injection system. In the worst of scenarios, it may even stop working altogether.
After you’ve found the fuel pump to be faulty, you may need to replace it. That’s if it can’t be fixed. Doing so restores the performance of the engine and improves drivability.
But when do you decide to install a new fuel pump and what’s the procedure for that? Whether to repair or replace this important component depends on the degree of damage and other factors.
In most cases, replacing the pump is necessary and almost inevitable. It’s a straightforward process and one that you can do yourself as we will see. Before we can look at how to replace the fuel pump, here are a few questions you might be asking and their answers.
How much does fuel pump replacement cost? This varies depending on the type, make and the brand of the fuel pump. However, the cost can be high if you choose to have a professional install the pump for you. Should you decide to do it yourself, the cost to replace your fuel pump can go down considerably.
How long does it take to replace a fuel pump? Again, that depends on many factors. If you’ve hired a mechanic, that make take a short time since they have the experience to do it. Also, if you’ve replaced one before, and you do not stop to think the next move. Usually, changing a typical fuel pump should take less than an hour.
If you’re replacing a mechanical fuel pump, you may not take much time. This type of pump is simple to install since there are not many parts to mind. The pump also mounts on the engine block which makes it easy to access. That’s unlike the electric pump that requires a whole module installed and sits hidden in a fuel reservoir.
How hard is it to replace a fuel pump? If you’re good at following instructions, fuel pump replacement should be easy for you. You only need to remove the old pump, install a new one, and that is it. You do not even need many different tools, as can be the case when servicing some vehicle parts.
Let’s now go straight to the replacement process, starting with the mechanical pump.
How to Replace a Mechanical Fuel Pump
Have with you these tools: A wrench set, pliers, and a bolt; you will use it to plug the fuel line to prevent fuel from flowing out
- Start by disconnecting the black wire from the battery. Its the one on the negative terminal and the ground cable
- Check the fuel line and replace it if damaged or worn out
- Release the pressure in the fuel tank
- Disconnect the hose from the fuel tank and plug it
- Disconnect the fuel line to the carburetor
- Remove the bolts mounting the fuel pump and remove it
- Remove any of the old sealants
- Apply a new sealer to the gasket on both sides
- Slip the gasket and the bolts in the new pump
- Install the new pump, making sure the actuating lever of the pump sits on the camshaft eccentric
- Connect the carburetor fuel line followed by the one to the fuel tank
- Tighten the bolts as appropriate
- Reattach the batteries ground
- Check for leaks
- Your fuel pump is now ready to send fuel to the engine. You may test it
How to Replace an Electrical Fuel Pump
Tools you will need: a wrench set, pliers, screwdrivers
- Find out how much fuel is in the tank by checking the fuel gauge. If it’s more than ⅛ full, you may have to reduce the fuel by siphoning it out
- Relieve the pressure in the fuel lines. You can do this by removing the fuel cap and the pump’s relay, then cranking the engine until it stalls in its own.
- Always attach the new pump firmly by tightening the bolts to the appropriate torque
- Disconnect the battery’s negative terminal or ground cable
- Remove the fuel tank’s cover to access the pump. If that’s not possible on your car, you may need to take out the whole tank
- Carefully remove the old and damaged fuel pump, together with its assembly
- Install the new fuel pump in its place
- Reattach the battery cable, the fuel pump relay, and the fuel cap
- Turn in the ignition for a few moments without cranking the engine. This is to pressurize the fuel lines. Repeat it a few times more
Fuel Pump Replacement Tips
Regardless of what type of fuel pump you’re replacing, you may need to keep to the rules. Doing so makes the process easier, quicker and above all, safer. Here are the tips to follow.
- Always relieve fuel pressure before beginning to install your new pump. Simply switching off the engine won’t help. You need to locate and pull out the pump’s fuse.
- Always disconnect the battery negative terminal cable before attempting to remove the fuel pump. You don’t want a fire to start and harm you.
- Always jack the vehicle appropriately if you have to go underneath it.
- If working with a fuel tank and fuel lines that contain a flammable liquid, observe safety measures. Don’t smoke or do anything else that could spark a flame or fire.
Sometimes, a fuel pump doesn’t need to be changed. That happens if the pump isn’t severely worn out or damaged. For fuel pump repair options, have a look at the next chapter.
Fuel Pump Repair
Sometimes, fuel pump problems are only slight. You may feel that the pump is repairable, even without the need to install a new one. You could also be on a budget and looking for a less expensive way to fix your fuel pump.
If that’s the case, you may want to know the options available and the advantages of each. That way, you can be in a better position to decide between fuel pump repair and replacement.
So what are these ways to restore a faulty fuel pump? That’s what we will look at in this chapter; how to fix a fuel pump without replacing it. At the end of the read, you will be in a position to determine what to do with your worn out of damaged fuel. And if looking to lower the costs, the right choice for your situation.
First, a look at the problems that can be fixed.
Fuel Pump Problems
In a mechanical fuel pump, the parts that usually wear out and make the pump less efficient are few. They include the diaphragm, filter, return spring and valves. When the pump has been around for several years, the diaphragm can become ruptured and leak fuel.
The pump’s strength then decreases, and its pumping action becomes faulty. The filter could also clog with dirt and cause a reduction of the pump’s efficiency. An old return spring can weaken, reducing the pump’s ability considerably.
If yours is an electric fuel pump, there are parts that will wear out over time and affect the pump’s action. These include the connections that corrode and increase electrical resistance. The motor of the pump is itself a delicate piece of equipment that although built to last, can break down to affect the pump’s performance.
The brushes in the motor do wear out too, especially if you’re fond of driving on low fuel levels. The armature, when it overheats, will eventually affect the pump’s operation. Other parts also weaken over time and cause the whole unit to malfunction.
Fuel Pump Repairs
Luckily, a majority of auto parts manufacturers do sell components to rebuild a bad fuel pump. Often in the form of a fuel pump repair kit, these components come ready to install and with the manual to do so. If you are hard pressed for cash or looking to extend the life of the fuel pump in your car, you may want to buy this kit.
It’s also worth noting that some damages can be repaired individually once you’ve determined what the matter is. Frayed wires to your fuel pump for example. You only need to replace them.
The Number One Cause of Fuel Pump Failure and How to Fix It
You may have heard that contaminated fuel can cause a fuel pump to fail. It’s true. Dirt and debris in fuel do clog the pump, reducing its ability to supply fuel to the engine. When that happens, the symptoms of a bad fuel pump become apparent.
You may hear the pump produce a whining sound when the engine idles. You could also experience frequent episodes of the car stalling while driving or engine sputters. These are the signs that the pump is working harder as a result of the clogging. Apart from affecting driving comfort and engine performance, the problem could cause the pump to burn out.
What Can You Do to Fix a Clogged Fuel Pump?
You cannot always control the purity of the fuel that enters your car’s fuel tank. Therefore, it’s essential that you find a way to ensure the pump doesn’t block as to cause reduced output. How can you do that?
By cleaning it with a fuel systems cleaner. These cleaners vary from one brand to another, but they work the same way. You can obtain a fuel system cleaner at any store that sells auto parts and it comes with usage instructions. Here are the steps to clean your fuel pump.
Cleaning the Electric Fuel Pump
Most pumps of this type have a fuel sieve at the point where fuel enters the device. This filter can get clogged and impair the pickup of fuel. These are the steps to unblock everything and restore the pump’s efficiency.
Things you will need: fuel systems cleaner, an open-ended wrench
- Run the engine to remove most of the fuel in the tank, or until you get the “empty tank” reading on the fuel gauge
- Pour the cleaner into the fuel tank. In most cases, you need to use all the amount in the bottle
- Fill the tank with fuel. This ensures that the cleaner distributes evenly ready to do its cleaning job
- Start the engine and allow it to idle
- The fuel will flow together with the fuel, through the pump, fuel lines, and to the engine, breaking down any dirt deposits in its way
- Let the engine idle for 10 and 15 minutes before driving. It will allow the cleaner to do the cleaning work in a thorough way
Cleaning the Mechanical Pump
A mechanical pump works differently, and may require a different method to rid its interior of dirt. If your car uses this type of pump, here is the procedure to clean it.
Things you will need: An open-ended wrench, a bowl to hold fuel that may spill
- Find and disconnect the battery’s negative terminal cable to prevent sparks while working
- Locate the fuel pump and which mostly mounts on the engine block
- Place a bowl underneath the pump to take care of any fuel spills. Ensure the container can hold the type of fuel that you use in your car
- Remove the fuel lines but only if they prevent access. Otherwise, there’s no need to
- Remove the pump’s top cover to expose the filter
- Using a clean brush, remove the debris covering the filter
- If the filter is the removable type, replace it
- Put the pump’s cover back
- If you had disconnected the fuel hoses, reattach them
With clogging being a leading cause of pump failure, these fuel pump cleaning procedures can be of great help. Pump replacement offers a lasting solution, but isn’t always possible or preferable. Some situations may call for a temporary fuel pump fix, as you wait for to install a new pump.
Whichever the case, it’s always advisable that you choose what will work for you. Also, what lies within your means or abilities. You may even decide to lower the fuel pump repair cost by adopting the DIY style. That way, you only need to purchase the repair kit, and you’re good to go.
We have reached the end of this guide for fuel pumps, and we have every reason to believe you found it useful. That you can now locate the fuel pump, take it out for servicing or replacement and test or check it for damage. Above all, you now understand how the fuel works and what effects it has on the engine when it malfunctions.
As a car owner, fuel pump knowledge can help you experience better engine performance. That is because you will easily tell when the fuel pump fails and fix it or replace it. The fuel pump means a lot in a vehicle. It is directly linked to the supply of fuel to the engine. A slight fuel pump fault can, therefore, disrupt the normal working of the engine and cause a vehicle to have drivability issues.