The operation of internal combustion engines, used in a variety of types of transport and equipment, is based on the combustion of a fuel-air mixture and the energy released as a result of this process. But in order for the power plant to function, fuel must be supplied in portions at strictly defined moments. And this task lies with the power system included in the design of the motor.
Engine fuel supply systems consist of a number of components, each of which has its own task. Some of them filter the fuel, removing contaminants from it, others dosage and supply it to the intake manifold or directly to the cylinder. All these elements perform their function with fuel, which still needs to be supplied to them. And this is ensured by the fuel pumps used in system designs.
Pump assembly
Like any liquid pump, the task of the unit used in the engine design is to pump fuel into the system. Moreover, almost everywhere it is necessary that it be supplied under a certain pressure.
Functional purpose
The operation of an internal combustion engine involves burning a fuel-air mixture in special chambers. The fuel system of a vehicle, the most important part of which is the pumping equipment, is designed to ensure an uninterrupted supply of fuel to the working components of the engine.
In the modern automotive industry, several types of fuel pumps are used. The simplest and, in today’s conditions, rarely used option is the traditional carburetor fuel pump . Its function is limited to moving fuel to the engine, and gasoline is supplied under normal pressure, and therefore this type of mechanism is often called a low pressure fuel pump or low pressure fuel pump.
The much more commonly used injection gasoline engine today uses a system of direct fuel injection into the cylinders. This involves supplying fuel under pressure. Therefore, the injector fuel pump is a fuel injection pump or high pressure fuel pump.
The design of a diesel engine provides for the presence of two fuel pumps at once. The first of them is the injection pump and is intended to move fuel from the tank to the injection pump . The latter, in turn, compresses the resulting fuel and ensures its delivery directly to the engine injectors.
Thus, the functions performed are determined by the type of engine and the fuel pump itself:
· the carburetor fuel pump supplies fuel from the tank to the engine without any pressure manipulation;
· the injector fuel pump, in addition to its transportation function, also builds up pressure before injecting fuel into the combustion chamber, and also doses fuel and regulates the frequency of its supply;
· The diesel fuel injection pump pumps diesel fuel from the tank into the engine;
· The injection pump of a diesel unit performs functions similar to an injector fuel pump - it builds up pressure, doses and determines the mode of fuel injection into the engine injectors.
Carburetor engine
First, a few words about the well-known mechanical fuel pump. It pumps fuel in cars with a carburetor. The key element is the membrane, which, by moving up and down, ensures the delivery of fuel from the tank to the carburetor. The design includes a valve system that ensures the injection of gasoline and prevents its return to the fuel line.
The movement of the mechanical parts is carried out directly from the engine itself; for this, where the fuel pump is located, its drive is provided in the cylinder block. Fuel can be pumped manually using the provided lever. The pump does not require an autonomous lubrication system, since it is included in a common line with the engine.
Classification
The most commonly used classification of fuel pumps - by engine type - was given above. However, other signs are also used that make it possible to divide the mechanism under consideration into types. For example, based on their location in the car, a distinction is made between submersible pumps, which are installed directly in the fuel tank, and pumps, mounted directly to the engine power unit.
Based on the type of drive, fuel pumps are divided into mechanical and electric. The first type is used in carburetor engines and older models of diesel units. An alternative option is used much more often today and is installed both in injection gasoline engines and in modern diesel power plants.
How does a fuel pump work?
The electric pump seems to push the supplied fuel inside the car engine. Fuel pump device
in older car models it is such that their unit operates at a fixed speed. New models are designed in such a way that the speed of the unit depends on the motor. The electric fuel pump depends directly on the electrical system of the car, which takes into account indicators such as the aero-fuel ratio, throttle position, and the amount of exhaust emissions contained.
Such units begin to work when the electric motor starts. When you turn the ignition switch, the on-board computer is activated and a signal is given to start the fuel pump. When an electric charge is applied, the motor inside such a pump begins to rotate, thereby creating pressure in the fuel system. If there is no engine signal for more than a few seconds, the fuel pump will be automatically turned off.
How does a fuel pump work?
, is heard during the first moments of starting a car engine. Next, gasoline enters the fuel pump through a tube and exits through a one-way valve, and then passes through the fuel filter into the car engine. While the engine is running, the fuel pump will also work.
The design of the car's power system and the operation of the fuel pump
Electric fuel pumps push fuel into the engine. The operation of the electric fuel pump is controlled by the vehicle's electronic system, which takes into account throttle position, air-to-fuel ratio and exhaust emissions.
Since electric fuel pumps operate under pressure, they are quite noisy and heat up quickly. It is for this reason that they are placed in the fuel tank - the fuel cools the fuel pump and muffles noise.
Features of the design of various types of fuel pumps
It is obvious that each of the types of fuel pumps listed above has characteristic design features, is designed to perform different functions and has significant differences in the principle of operation. Therefore, it is advisable to consider each of them in more detail.
Mechanical carburetor fuel pump
A standard mechanical type fuel pump is installed on the engine - usually on the cylinder block. It is attached using regular screws. The operation of the mechanism is ensured by the movement of the so-called cam eccentric.
The design of a mechanical fuel pump includes the following elements:
- the housing, inside which the remaining parts are located;
- a pusher directly connected to the mechanical drive cam;
- lever and rod, which receive energy from the rod and ensure the functioning of the pump;
- a membrane that divides the internal space of the pump into two chambers - inlet and outlet;
- a return spring designed to return the rod to the starting position;
- two valves installed on the discharge and suction channels;
- a filter, which in most models is also located inside the pump housing and is designed to clean the fuel supplied to the engine.
In the modern automotive industry, mechanical fuel pumps are used quite rarely, which is explained by their lower efficiency compared to electrically driven units. However, they have a number of significant advantages, including: a simple and reliable design, as well as the ability to manually pump fuel, which makes it possible to start the car without problems after a long period of inactivity.
Electric fuel injector pump
Electrically driven fuel pumps are installed not only on gasoline injectors, but also as fuel injection pumps on diesel engines. The demand for electric gasoline pumps has led to the emergence of several varieties of this type of mechanism, differing in design features. These include the following types of fuel pumps:
- vacuum _ The design of the unit as a whole is similar to the mechanical fuel pump described above. The only significant difference is the replacement of the eccentric with an electric drive. The latter works as a pull-in relay, which has two components - a core and a winding;
- roller _ The working unit of this type of fuel pump consists of a rotor with special grooves into which rollers are installed. The movement of fuel is achieved by rotating the rotor and changing the distance between it and the rollers. The electric drive is a conventional DC motor;
- gear . The supply and increase in fuel pressure in this case is achieved through the rotation of a rotor made in the form of a gear and located eccentrically to another gear, which is called a stator. The teeth of both gears form chambers, the volume of which is constantly changing, due to which pressure differences are created and fuel is supplied to the engine;
- centrifugal . The working unit of the pump is a wheel equipped with blades. Due to their movement, turbulence is created, as a result of which the fuel is transported from the suction channel to the discharge channel;
- plunger _ This type of fuel pump design is rarely used for gasoline engines and is much more often used in diesel power plants in fuel injection pumps. The mechanism is based on plunger pairs, consisting of a sleeve and a piston, which are driven by a cam shaft. Moving the plunger builds up pressure in the space above it and supplies fuel to the engine injectors.
Electric fuel pumps are divided into two types - remote and submersible. The first type is installed on the vehicle body, and the second is mounted directly in the fuel tank. In modern car models, submersible fuel pumps are more often used. The key advantages of this arrangement are the absence of the possibility of so-called “dry running” and cooling of the unit due to immersion in the working fluid.
TNND diesel
The low pressure fuel pump of a diesel engine is designed to perform one function - transporting fuel from the tank to the injection pump. On older models of power plants, mechanical fuel pumps were used in a similar capacity. Modern diesel units involve the use of high pressure fuel pumps with an electric drive.
Diesel engine injection pump
The main feature of a diesel engine is the supply of fuel under high pressure. To successfully perform this function, fuel injection pumps are used. Modern models of fuel pumps of this type are designed to solve two more important problems, which include: fuel dosage and regulation of the frequency of its injection into the combustion chambers. It is the successful implementation of the three listed functions that largely determines the efficiency and efficiency of the operation of a diesel power plant.
The main working unit of the fuel injection pump of a diesel engine is a plunger pair. Its device consists of two elements - a piston or plunger, which moves inside a sleeve, often called a sleeve. High-strength steels are used to manufacture the plunger pair, and the working surfaces of the parts are made with high precision and carefully processed. As a result, a tight connection is achieved while simultaneously allowing the piston to move inside the sleeve.
In the modern automotive industry, three types of fuel injection pumps are used:
- classical _ The device and principle of operation generally resemble the injector fuel pump described above. Fuel is supplied via plunger pairs directly to the diesel engine injectors;
- pump-injector or pump- dus system . The main design feature of this type of injection pump is the presence of a special pumping device installed on each injector. This allows you to increase engine power compared to a standard injection pump by 5-6%. The downside of the system is that it is demanding on the quality of the diesel fuel used by the engine;
- common rail system . The most progressive type of fuel injection pump for diesel units, widely used in recent years. This type of fuel pump design provides a common rail from which fuel under very high pressure is supplied directly to the injectors. The use of common rail ensures the highest possible diesel efficiency, which is combined with the efficiency and environmental friendliness of its operation.
Service life and main malfunctions of fuel pumps
Regardless of the type of fuel pump, the main factor influencing the durability of the mechanism is the quality of the fuel used during operation. This applies equally to both gasoline and diesel units. The main problem that arises when the pump operates in such a situation is contamination of individual parts of the fuel system. A partial solution to this problem is the use and regular replacement of effective cleaning filters.
Another common cause of submersible fuel pump failure is operating the engine with a small amount of fuel in the tank. In this case, it becomes difficult to cool the unit, which leads to its overheating, reduced efficiency and, in the worst case, simply failure.
The main criteria for diagnosing a malfunction of a car’s fuel pump are the following:
- difficulty starting the engine;
- increased fuel consumption and increased volume of exhaust gases;
- reduction in engine power at high speeds or changes in the operation of the power plant;
- the occurrence of extraneous sounds when starting and operating a gasoline or diesel engine.
Modern diagnostic equipment effectively identifies possible problems in the early stages. This allows you to take the necessary measures to eliminate them, as a result of which, at a low level of costs, the standard service life of the fuel pump is significantly increased. In addition, it is possible to avoid much more serious costs for repairs and replacement of components or parts that have become unusable.
