Fuel Pump: Definition, Meaning, Construction, Working, Types

In this article, we will learn what is fuel pump, how it works, definition, meaning, applications, etc.

Let’s explore!

What is Fuel Pump? Definition

Fuel Pump Definition

A fuel pump is a component in automobiles that distributes liquid from the fuel tank to the internal combustion engine’s carburetor or fuel injector.

Fuel Pump Meaning

The fuel pump was invented in 1920 because it became a demand of the society and people before 1920 used gravity as a major tool for making petrol to reach the carbonator. The gasoline tank was placed above the engine, as seen in the diagram.

The feed pipe was designed to allow fuel to drip down to the carburetor. Back in the day, some automobile owners would put a handmade petrol filter in the feed pipe. This design was utilitarian, but it was also dangerous. Keeping the gasoline tank near to the engine is unsafe.

A fire might start if there is a gasoline leak and the engine is heated. The word firewall comes from a time when the gasoline tank was placed above the engine.

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Construction & How Does Fuel Pump Work?

A cam and tappet mechanism at the bottom drives the plunger. This mechanism pertains to a rotating cam, a tappet, a roller rotatably placed on the tappet for cam cooperation, and a plunger part which is directed for movement in a plane approximately at right angles to the cam’s axis of rotation, said par being touched by the tappet to accomplish said movement.

After using such mechanisms, it has been discovered that tracking of the cam and roller surfaces occurs, indicating that the roller surface is not bearing correctly against the cam surface, and the purpose of this invention is to offer such a mechanism in a manner that minimizes tracking. According to the innovation, in a mechanism of the type described, the roller is annular in shape and has a cylindrical outer surface and a spherical inner surface, the roller is placed about an annular part carried by a pin guarded to the tappet, and the annular part has an outer surface complementary to the internal surface of the roller, allowing the roller’s axis of rotation to move relative to the pin’s axis furthermore, the roller may be hollow cylindrical in shape, with an intermediate annular portion placed between the roller and the first described annular part, with internal and exterior peripheral surfaces complementary to those of the roller.

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In the barrel, the plunger reciprocates. The number of plungers in the engine is equal to the number of cylinders. A rectangular vertical groove runs the length of the plunger. Under the pressure of the gasoline on the spring, the delivery valve is raised off its seat. The injector  in fuel pump receives the fuel from the delivery valve. When the plunger reaches the bottom of its stroke, the supply port and spill are exposed, and fuel from a low-pressure pump is pumped into the barrel after filtration. The plunger has now been forced up by the cam action, and both sections have been closed. The fuel above the plunger is compressed as the plunger moves farther, lifting the delivery valve and directing the gasoline to the injector.

The plunger rises even higher, and at a certain point, the helical groove connects the spill port to the fuel in the top half of the plunger via the rectangular groove. As a result of the quick pressure reduction, the delivery valve is forced back into its seat by the spring force. In addition, the pressure in the delivery pipe decreases. As a result, the injector’s nozzle discharge is abruptly shut off. The loop keeps repeating itself. The time of each plunger stroke varies depending on whether the spill port is designed to transmit the high-pressure gasoline in the top section of the barrel earlier or later. This is determined by the helical groove’s location, which may be adjusted by spinning the plunger with the rack. The accelerator is linked to the rack. It corresponds to a geared quadrant. The rack’s rotation causes the gear quadrant to revolve, which then causes the plunger to rotate. The driver just has to manage the gasoline delivery to the engine cylinder by pressing the accelerator pedal.

Fuel pump Toyota corolla  has been one of the most perfect cars having best fuel pumps. Fuel pumps of Toyota corolla are preferred by all the dealers who are in the business of fuel pumps.

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Types of Fuel Pumps

The types of fuel pumps are based upon the performance of the fuel. Pressure, volume, and vacuum are used to evaluate the performance of the fuel. On the outlet side, a pump must provide a particular pressure as stipulated by the manufacturer. Connect a pressure gauge between the pump and the carburetor and run the engine at a predetermined speed to test a pump for pressure. The pressure generated by the petrol pump will be displayed on the gauge. Disconnect the petrol from the carburetor and run the engine at idle speed for the volume test. Collect the fuel that comes out of the pump in a separate container to measure the volume. So there  are two types of fuel pumps

  • Mechanical fuel pump
  • Electrical fuel pump

What is Mechanical Fuel Pump? Parts, Working, Construction, Advantages & Disadvantages

Let’s see the different parts of mechanical fuel pump.

Parts of Mechanical Fuel Pump

The components of mechanical fuel pump include

An eccentric or cam

On a mechanical gasoline pump, the eccentric pull the arm up and down. Some engines were designed to work with mechanical gasoline pumps but were never utilized with them, leaving them with an eccentric that was unnecessary. A person doesn’t need eccentric if his car has efi, but if you remove it, you’ll need to replace it with a thick washer.

A diaphragm

A diaphragm pulls gasoline from the gas tank and pushes it toward the engine. When the diaphragm of a mechanical gasoline pump is broken or wears out, it can cause the pump to stop working correctly or completely.

A pull rod

It is a solenoid that attracts an iron rod that pulls the diaphragm down, drawing petrol into the chamber.

A strainer

The strainer on the gasoline pump is not a moving item. The fuel pick-up tube is covered by a very fine mesh filter. The fuel pump draws fuel from the tank at this point. Only clean gasoline may enter the fuel pump due to the existence of the fuel pump strainer.

An inlet valve

The pump’s cylinder walls include inlet and exit ports on two sides, enabling fuel to flow into the compression chamber until the plunger is pulled up, shutting the two ports and commencing the compression action.

A pressure valve

The pressure regulating valve (prv) is a type of control valve that regulates a consistent pressure within the fuel pump, ensuring the safety of all fuel system component

An outlet valve to carburettor

It is the valve with help of which the fuel moves to the carbonator.

Construction and working of a mechanical fuel pump

A mechanical fuel pump is driven by the camshaft or a specialized shaft powered by the crankshaft. As the shaft spins, a cam passes beneath a pivoted lever, driving it up at one end. The other end of the lever, which is loosely linked to a rubber diaphragm that forms the chamber floor of the pump, lowers, dragging the diaphragm behind it. When the lever pulls down on the diaphragm, it creates suction, which draws fuel into the pump via the fuel line. A one-way valve is a valve that allows just one flow direction. As the rotating cam spins faster and no longer pulls on the lever return spring, the lever is moved back, freeing its hold on the diaphragm.

The diaphragm is not pushed up by a loosely attached lever, but it is pressed upon by a return spring. Only by discharging fuel from the diaphragm can it travel higher. Chamber. Because the gasoline cannot return through the first oneway valve, it must exit through a second one. The carburetor is a device that controls the flow of fuel through the engine. Only gasoline is allowed into the carburetor. Through the needle valve in its float chamber, it requires it; no fuel exits the pump when the carburetor is full and the needle valve is closed. The diaphragm remains pressed on the lever, which moves up and down. When the carburetor receives additional gasoline, the return spring pushes the diaphragm up, bringing it back into touch with the lever, which pulls it down to refill the pump chamber by taking up the slack in the loose connection.

The force produced by the diaphragm spring consequently limits (and hence regulates) the pressure at which the gasoline is ejected from the pump. To pull the fuel through the pipes, the pump produces negative pressure. Low pressure between the pump and the fuel tank, along with heat from the engine and/or hot weather, can cause the gasoline in the supply line to evaporate. This causes fuel starvation because the fuel pump, which is meant to pump liquid rather than vapor, is unable to take in additional fuel, leading the engine to stall. This is distinct from vapor lock, in which excessive engine heat on the pressurized side of the pump (between the pump and the carburetor) boils the gasoline in the lines, depriving the engine of sufficient fuel to function.

Advantages of a mechanical fuel pump


It is a very simple pump with a very common working phenomenon among car repairers. Their fixing procedures and assembling procedures are well known among the car mechanics so if you face any issue you don’t have to travel long to find ab electrician to repair your car. Rather than an ordinary mechanic will be able to fix it


It is reliable as we see the electronic parts which require electric current, they are less reliable because sometimes any short circuit happens sometimes the excess of current burns the coil so these mechanical fuel pumps are more reliable than electric fuel pumps

Disadvantage  of mechanical fuel pump

The mechanical fuel pump is having a very dangerous disadvantage in that the fuel pump is situated within the vicinity of an engine which can cause a burn fire due to leakage and overheating of the engine. This can be very fatal because it can cause a life-threatening situation

Applications of a mechanical fuel pump

Mechanical pumps are being used less and less with time, and are mostly found in older vehicles. This sort of fuel pump will not be found in almost any new or even newer car. They will eventually be phased out because modern cars do not require them. Because the fuel is pumped into the carburetor by a mechanical fuel pump, the fuel delivery efficiency is slowed. With autos, fuel injection has become the more modern source. The fuel is pumped at a higher pressure, which will aid in its delivery in the most effective manner feasible.

What is Electrical fuel pump? Parts, Working, Construction, Advantages & Disadvantages

On engines with fuel injection, an electrical fuel pump is utilized to pump fuel from the gas tank to the injectors. To allow the injectors to spray the fuel into the engine, the pump must provide the fuel at high pressure (usually 30 to 85 psi depending on the application)the high pressure is very important because at low pressure the car starts missing and it feels as the petrol has been finished so for the engine to work properly, the fuel pressure must be within limits. Insufficient fuel pressure can cause the engine to run low, misfire, pause, or stall. Excessive fuel pressure can make the engine run rough, waste gasoline, and damage the environment. Although the majority of electric fuel pumps are located within the gasoline tank, others are located outside. Some automobiles may even have two petrol pumps (one within the tank and one outside the tank).

There is a petrol pump outside. The in-tank location muffles the humming. Creating noise from the electric pump motor, and submerging the electric pump motor by pumping in gasoline, the pump motor is lubricated and kept cool. When driving with a pump, if the gasoline tank is less than 1/4 full, the life of the pump will be affected. If the car runs at a fast pace it also boosts the likelihood of the pump becoming momentarily depleted. Running out of gas can sometimes affect the fuel pump. Electric fuel pumps should be kept submerged in the gasoline tank. The working and efficiency of the fuel tank are affected by the reduced amount of gasoline in the fuel tank the pump is normally included in the sending unit assembly, which also includes a float that provides an electrical signal to the instrument panel’s fuel gauge. If you need to replace an electric fuel pump, you can do it as a single component or as a whole module assembly (which is more expensive but easier and less bothersome).

Electric fuel pumps are available in a range of styles. A positive displacement “roller cell” pump is used in some older applications. Rollers are positioned on an offset disc that revolves inside a steel ring in this kind. From the pump intake to the exit, fuel is sucked into the gaps (cells) between the rollers and pushed along. This type of pump can produce extremely high pressure and has a consistent flow rate. However, because the output is in pulses, a muffler is frequently installed after the pump to attenuate pressure pulses. A roller cell pump can also be put outside the gasoline tank and used in conjunction with a low-pressure supply pump installed within the tank. The “gerotor” pump is another form of positive-displacement pump. This pump is similar to an oil pump in that it employs an offset rotor to push gasoline through it. The roller vane pump is another option. Instead of rollers, vanes are employed to force gasoline into the pump.

A “turbine” design fuel pump is used in the majority of modern automobiles. An impeller ring is linked to the motor of a turbine pump. As the impeller rotates, the blades of the impeller push the gasoline through the pump. Because this is not a positive-displacement pump, it does not create pulsations and works smoothly and silently. It runs at a faster rate and uses less electricity than earlier pumps. It’s also less difficult to make and lasts a long time. This type of pump is used by certain aftermarket pump suppliers to replace earlier pumps.

Working of an electric fuel pump

Electric pumps are classified into several categories based on their operating principles. In-tank electric fuel pumps, on the other hand, function on a similar premise. The powertrain control module (pcm) energizes a relay that delivers voltage to the fuel pump when the driver switches on the ignition key. To develop pressure in the gasoline system, the motor within the pump starts spinning and operates for a few seconds. The length of time the pump runs before the engine starts is limited by a timer in the pcm. An intake tube and mesh filter sock are used to pull fuel into the pump (which helps keep rust and dirt out of the pump). The fuel is then pumped toward the engine through the fuel line and filter after exiting the pump through a one-way check valve (which preserves leftover pressure in the system when the pump is not functioning). The fuel filter captures any rust, dirt, or other solid pollutants that may have traveled through the pump, preventing the fuel injectors from becoming clogged. The fuel is then transported to the individual fuel injectors through the engine’s fuel delivery rail. Fuel pressure is maintained via a fuel pressure regulator on the gasoline rail, which also sends surplus fuel back to the tank.

The fuel pressure regulator is positioned in the gasoline tank and is part of the fuel pump module on modern cars with return-less efi systems. From the engine to the tank, there is no gasoline return line when the engine begins, the fuel pump operates constantly and continues to run as long as the engine is running and the ignition key is turned on. The pump may function at a steady speed or at a variable speed based on engine load and speed. The pcm will detect the lack of the rpm signal and turn off the pump if the engine fails. Many cars, including fords, include an “inertia safety switch” that turns off the fuel pump in the event of an accident. This is done to lessen the possibility of a fire if a fuel line ruptures. The safety switch is tripped, and the fuel pump circuit is opened. After the event, the safety switch had to be manually reset by pressing the reset button on the switch. The gasoline pump on older automobiles works at a steady pace. However, on many contemporary applications, the pcm adjusts the pump speed to better match the engine’s fuel demand.

Uses of electric fuel pumps

Electricity as a source of energy pumps are frequently employed in engines that demand a high level of pressure. Electric fuel pumps are used in vehicles with fuel injection systems. Electric gasoline pumps are the most often utilized pumps nowadays.

Disadvantages of electric fuel pumps

Engine sputters at a high speed

When driving a vehicle at a constant high pace, the most typical early indicator of a fuel pump malfunction is when it stops working. The car will drive ok for approximately 10 miles down the road before jerking about or sputtering, for a mile or two before returning to normal. Many individuals wrongly believe that a sputtering car has “dirty” gas or another fuel-related problem. While this may be the case, a weary fuel pump is more likely to cause this symptom as it strains to give a consistent stream of gasoline to the engine at the right pressure. The engine sputters due to a lack of pressure.

Vehicle loses power while accelerating

This second symptom produces sensations that are extremely similar to the first. Vehicles, rather than experiencing sputtering while driving, will suffer it when accelerating from a stop. In most cases, the car will move at first before producing sounds and jerking about as if it is about to stall. Then it will easily continue on its accelerated path: the engine’s requirement for gasoline increases as the process of acceleration progresses. A faulty fuel pump, once again, is unable to maintain the appropriate pressure to supply this fuel in a consistent manner, leading the engine to mix fuel and air incorrectly and lose power. The engine is able to function smoothly after the pressure is restored.

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Hence damaged fuel pumps though results in engine sputtering and losing power but they are very important to a vehicle  because that distributes fuel from the fuel tank to the engine.


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