The fuel pump is one of the most important parts of the fuel system. The efficient working of the fuel pump ensures the proper supply of fuel to the engine. This article explains the fuel pump working, types, and applications.
What is a Fuel Pump?
A fuel pump is part of an automobile that supplies fuel from a fuel tank to the carburetor of an IC engine. A fuel pump is an important part of the IC (Internal Combustion) engine. This is because the fuel supply is important to keep the engine running.
Whether you’re trying to breathe new life into a large piece of carbureted block or running a lawn device, the engine requires a stable fuel delivery, which is the purpose of the fuel pumps.
The carbureted engine generally uses a low-pressure mechanical pump located outside of the fuel tank, while a fuel injector engine generally uses an electric fuel pump.
Electric fuel pumps use in engines that are equipped with a fuel injector to transfer fuel from the fuel tank to the fuel injector. According to the use, these pumps must supply fuel at high pressure (typically 30-85psi) for the fuel injector to inject fuel inside the engine.
The pressure of the fuel must be according to the requirements for the engine to operate normally. If the pressure is too low, the engine will run out of fuel, causing the engine to stall, hesitate, misfire, or lean. If the fuel pressure is too high, the engine will not run properly, fuel will be wasted, and contamination will have appeared in the fuel.
Driving with a fuel tank with less than 0.25 fuel will overheat your engine and reduce the pump’s life. It can increase acceleration, braking, and sharp turns which also increase the risk of temporary starvation of the pumps for fuel. Exhaust gases can lead to improper lubrication and cooling of the electric fuel pumps and can damage the pump.
Types of Fuel Pumps
There are two significant types of fuel pumps:
- Mechanical Fuel Pumps
- Electrical Fuel Pumps
1) Mechanical Fuel Pump
Before the common acceptance of electronic fuel injection, maximum automotive gasoline engines used mechanical fuel pumps to move fuel from the fuel container to the carburetor bowl.
The mechanical fuel pumps are driven by the eccentricity of the engine’s camshaft. The mechanical fuel pump is located on the side of the in-line cylinder block engine.
The plunger-type and diaphragm pumps are the most commonly used mechanical fuel pumps. The diaphragm pump is a famous positive displacement pump. This pump contains a pump chamber, the volume of which increases or decreases due to the deflection of the flexible membrane, similar to a piston pump.
Do you know: What are different types of Pumps?
Mechanical Fuel Transfer Pump Working
A mechanical fuel pump is driven by a camshaft or a special shaft that is driven by a crankshaft. When the shaft rotates, the cam goes under the pivot level and pushes the shaft up at one end.
The lever’s other end loosely connects to the rubber diaphragm that forms the bottom of the chamber floor of the pump, moves downward, and is used to pull the diaphragm.
As the lever forces the diaphragm downward, a suction force is created that pulls fuel inside the pump by a check valve along the fuel pipeline. When the rotating cam continues to rotate and no longer pushes the lever, the return spring moves the lever back and releases its tension on the diaphragm.
The loosely connected lever doesn’t force the diaphragm upward, but the return spring pushes against it. This diaphragm or membrane can only be moved upwards by draining gasoline from the engine’s chamber.
Gasoline cannot be returned from the 1st check valve, so it drains into the carburetor through another valve. The carburetor draws gasoline from the float chamber needle valve only when needed.
2) Electric Fuel Pump
Electric fuel pumps are used in modern vehicles to deliver fuel from the fuel tank to the engine. An electric fuel pump uses electrical power and typically uses a motor to rotate a piston or diaphragm that transfers the fuel.
The electric fuel pumps are installed in the fuel tanks. This pump generates high pressure in the fuel pipes and pushes gasoline/petrol into the engine. The higher the pressure increases the gasoline boiling point.
These types of fuel pumps operate continuously while the engine is working. The powertrain control module (PCM) of your vehicle regulates the working of this pump. The computer monitors the fuel pressure and adjusts the pump’s operation to ensure that the engine is receiving the correct amount of fuel.
The main advantage of installing electric fuel transfer pumps inside the fuel chamber is that it is less prone to fire. Electric parts (like fuel pumps) generate sparks and ignite fuel vapors, but liquid fuel does not detonate. For that reason, immersing the pump in a fuel chamber is one of the most important places.
Changing the mechanical pump with an electric fuel pump can reduce the stress on the engine parts and reduce the fuel consumption of the engine.
If the pump runs incessantly, you can switch off the engine with a signal to save fuel. However, the required fuel pressure is still accessible for a fast start.
Read Also: Different types of Engines
Electric Fuel Pump Working
As the driver switches on the ignition key, the Powertrain Control Module (PCM) turns on the relay that powers the fuel pump. The rotation of the pump’s electric motor initiates, and it rotates for some time to increase the fuel system pressure. The PCM timer limits the amount of time in which the pump will operate before the engine starts.
After this process, fuel introduces into the pump by a suction valve and filter mesh socks (which prevents dust and rust from getting into the pump). After that, the fuel leaves the pump by a check valve (when the pump is not running, a check valve sustains residual pressure inside the engine) and is forced to the engine through a fuel pipeline and filter.
This filter catches dust, rust, or other solid debris that may have to go through the pump. It removes contaminations to prevent the fuel injector from blockage.
After passing through the filter, the fuel goes into the engine’s fuel supply rails and feds to various injectors. The purpose of the fuel pressure regulator is to maintain fuel pressure and returns additional fuel to the fuel chamber.
After starting the engine, the electric fuel transfer pump continues to run. This pump continues working as much as the engine is operating and the ignition key is switched on.
The pump can work at a steady or variable speed according to the engine speed and load. If the engine stops, the PCM detects a loss of the speed signal and switches the pump off.
Many cars (e.g., Ford) contain an “inertial safety switch” that turns off the pump in the occasion of an accident. This switch is attached to vehicles to decrease the fire risk if the fuel line breaks.
Advantages of Electric Fuel Pumps
- Availability or Accessibility: If you are working on a private car, it is better to choose the type of pump that is most suitable for your car. However, it is more likely that you can find a general-purpose pump at your local parts store in many cases. Fuel pumps are readily available in the market and almost all spare parts workshops. Unfortunately, if your engine’s pump is damaged, then you can easily find a new pump at your nearest workshop. The accessibility of these pumps is very easy.
- Reliability: Electric fuel pump has more reliability than mechanical fuel pumps.
- Improved engine starting: Electric fuel pumps help to build up fuel pressure in the fuel lines quickly, which can make it easier to start the engine, particularly in cold weather.
- Safety: The location of the fuel pump system can be a problem. These are usually located near the distributor head or the exhaust manifold. The remaining heat can trap vapors or boil fuel in the system and cause a fire. The usage of electric pumps is the only way to solve these problems. These pumps provide high safety to the vehicle engines.
- Higher flow rate: A higher fuel rate is necessary when dealing with replacing fuel injection or high-power levels. Although a mechanical pump can provide the required fuel flow, an electric fuel pump of the same performance is easy to install.
- Pressure: The working pressure of the mechanical fuel pumps is from 4 to 6 PSI. In contrast, electric fuel pumps can operate at pressures from 30 to 40 PSI.
- Easy to install: These fuel pumps are relatively easy to install.
Applications of Fuel Pumps
- Vehicles: Fuel pumps are most commonly used in various vehicles to transfer fuel from the tank to the engine.
- Agriculture: These pumps are also employed for various agricultural machinery such as a tractor.
- Marine: Fuel pumps are employed in ships and other marine vessels to transfer fuel from the fuel tank to the engine. These pumps have the ability to bear the harsh marine atmosphere. These pumps may also be installed outside the tanks.
- Aircraft: They are also used in airplanes to supply fuel from the tank to the engine. The fuel pumps used in aircraft are planned to work at low temperatures and high altitudes.
- Industrial Applications: Fuel pumps are used in different industries to move fuel or other liquids between containers or to deliver fuel to burners or engines.
FAQ Section
What is the difference between a lift pump and a fuel pump?
Modern fuel pumps enable vehicles to run their fuel injection systems faster and reduce fuel consumption. Lift pumps help increase the amount of fuel entering the engine block and add it to the system by creating suction and controlling airflow.
Is an electric fuel pump more efficient than a mechanical Pump?
Electric pump solves many problems that cam-driven pumps can’t solve and is required for numerous functions. However, compared to similarly priced electric pumps, mechanical pumps can provide adequate fuel flow. A mechanical pump has more excellent reliability than an electric pump.
Is a fuel pump available in a diesel engine?
Depending on the engine type, the diesel pump can be accountable for the diesel exhaust, and the fuel pump can also be accountable for the petrol exhaust. Both diesel and petrol engines are IC engines. That is, both use an air-fuel mixture that powers the vehicle after ignition.
Can we use a carburetor with an electric fuel pump?
The answer is yes. Various electric pumps are designed for carbureted applications. Some vehicles like the Chevrolet Vegas are made with electric fuel pumps. You just need to make sure that it’s correct and adjust the fuel flow according to your carburetor’s needs.
Does the electric fuel pump need a regulator?
Most lever-operated mechanical fuel pumps do not need a regulator. In contrast, some electric fuel pumps have a built-in regulator, so there is no need to buy external equipment. These pumps are typically manufactured to operate with carburetors because they have low pressure.
What is the best place to install an electric fuel pump?
The electric pump should be installed as close to the tank as possible and as low as doable. These constructions are intended so that fuel can push quickly. Therefore, it is important to minimize the distance to the fuel delivery while gravity helps in the supply to the pump.
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