Diagram of the fuel system of the engine from A to Z. Diagram of the fuel system of a diesel engine and a gasoline engine

The fuel system is an integral element of any modern car. It provides the appearance of fuel in the cylinders of the engine. Therefore, fuel is considered one of the main components of the entire design of the machine. In today's paper will be considered the scheme of the fuel system, its structure and functions.

Appointment

The main function of this unit is to supply the internal combustion engine with a certain amount of fuel. Previously, before this, it passes several stages of purification and is fed into the cylinder under pressure.

Node device

Strangely enough, but the scheme of diesel fuel system is very similar to gasoline analogues. The only difference is in the injection system. But we'll talk about this a little later, but for now, let's consider the design of this node.

So, the scheme of the fuel system assumes the presence of the following structural elements:

• Fuel tank . This element can be made from sheet steel or from very dense polypropylene. On passenger cars and off-road cars the gas tank is installed on the bottom. On trucks, in particular tractors, it is mounted on special supports between the rear and front axle (on the left or on the right side). In the fuel tank there is a valve preventing the fuel from escaping when the vehicle is tipped over.
• The filler cap . This part has a special thread, which makes it possible to let in air when it is unscrewed. And in order for the driver to conveniently unscrew the lid, it provides a special ratchet mechanism. Also in this element there is a safety valve, which when the car hits an accident, relieves pressure inside the tank. By the way, on modern cars with the standard of exhausts "Euro-2" and more, fuel vapor is not allowed to enter the atmosphere. Therefore, to capture them, a special coal adsorber is installed in the system.
• The fuel pump . This element has an electric drive and is located inside the tank. The pump is controlled by an electronic control unit. The part is activated by means of a special relay. When the driver turns on the ignition, it works for a while (no more than 4-5 seconds), thereby providing the necessary pressure in the system to start the engine. It is also worth noting that the pump is cooled by gasoline. Therefore, working with an empty tank can disable it.
• The fuel filter . Often, a car is supplied with two types of data elements. This is a mechanism for fine and coarse fuel cleaning. The strainer is mounted on the fuel pump housing. The essence of his work consists in the detention of contaminants, which can get into the engine and form an excessive deposit. Also, a serviceable filter significantly increases the life of the pump, preventing its frequent contamination. The fine cleaning mechanism is located on the bottom of the body, in front of the rear suspension of the car. This type of filter is based on a paper element that can hold small particles of dirt, tar and deposits that can damage the fuel system.

Fuel Level Sensor

It is located on the pump module. By its design , the fuel level sensor is a small system consisting of a float and an alternating resistance mechanism with nylon contact. Depending on the amount of content in the fuel tank, the resistance of the element changes, which fixes the arrow on the instrument panel in the cabin. It should be noted that the gasoline sensor is not exposed to the negative impact of substandard fuel additives and does not break with frequent changes in temperature and pressure inside the tank.

Ramp

This element consists of four nozzles, each of which has its own choke. The ramp is installed on the intake manifold and performs the function of supplying fuel to each cylinder.

Injectors

This detail is of special importance for the car, since it depends on its condition that the combustion quality of the fuel-air mixture depends on the consumption and power of the vehicle. The nozzle is a small mechanism with a solenoid valve. The latter is controlled by the computer. When the control unit commands the supply of power to the coil of the injector, the closed ball valve is opened and the fuel passes through the plate into the nozzles of the injector. By the way, on the plate there are holes used to adjust fuel consumption. The fuel is injected by the injector into the channel of several intake valves. As a consequence, it evaporates before it enters the combustion chamber of the engine.

Types of fuel supply systems

For today it is accepted to distinguish several types of fuel systems, which are used on diesel and gasoline engines. In particular, the fuel supply system of gasoline internal combustion engines is divided into two types and can be carburettor or injector. Both types have their differences in design and principle of operation.

Features of the carburetor

The main difference of this fuel system from the injector is the presence of a special mixer. His name is a carburetor. It is there that the fuel-air mixture is prepared. The carburettor is mounted on the intake manifold. To it the fuel which is sprayed further by means of jets and mixes up with air is brought. The finished mixture is fed to the manifold through the throttle valve. The position of the latter depends on the level of engine load and the frequency of its revolutions. By the way, the diagram of the fuel system of the gasoline engine is presented in the photo below:

As you can see, a lot of electronic sensors are involved in the preparation and combustion of the fuel mixture. Of particular importance for the car is the throttle position sensor and crankshaft speed sensor.

We also note that the scheme of the fuel system (UAZ "Buchanka" including) carburetor type differs by a low level of pressure, which is formed when fuel is injected. The very same supply of gasoline to the cylinders of the engine is done by gravity, that is, when the pressure in the combustion chamber decreases when the piston moves to the NMT.

Features of the injector

The scheme of the fuel system ("Mercedes e200" including) of the injector type has a fundamental difference from the carburetor analog:

• Firstly, the fuel from the tank in it is fed to the ramp to which the spray nozzles are connected.
• Secondly, the air into the combustion chamber of the engine is fed through a special throttle assembly.
• Thirdly, the level of pressure created by the pump in the system is many times greater than that created by the carburetor mechanism. This phenomenon is explained by the need to ensure rapid fuel injection nozzle into the combustion chamber.

But not only this is different from the carburettor fuel injection system. "Chevrolet Niva" (the scheme of its fuel is shown in the photo below), like other modern cars, has at its disposal the so-called "electronic brains", that is, the ECU. The latter is responsible for collecting and processing information from all existing sensors in the car.

So, the ECU also manages the injection of gasoline. Depending on the mode of operation, the electronics independently determines which mixture should be fed into the cylinder - poor or enriched. But not only this differs the scheme of the fuel system ("Ford Transit" CDi including) of the injector type. It can have a different number of nebulizers. We will discuss this in the next section.

Scheme of fuel injection on injection cars

At present, there are two types of injection systems:

• Mono-shot.
• With distributed injection.

In the first case, fuel is supplied to all cylinders using a single injector. At the moment, mono-shot systems are almost not used on modern cars, which can not be said for cars with distributed injection. The peculiarity of such injectors is that each cylinder has its own, individual injector. This installation scheme is very reliable, and therefore it is used by all modern automakers.

How does the injector work?

The principle of operation of this system is very simple. Fuel from the tank under the action of the pump is fed to the ramp (in it the fuel is always under high pressure). Then it goes to the nozzles, through which the spraying into the combustion chamber is carried out. It is worth noting that the injection is not constant, but at certain intervals. Simultaneously with the supply of fuel, air enters the system. After the fuel mixture has been mixed in a certain proportion, it enters the combustion chamber. The process of preparing the mixture on injectors is several times faster than in carburetor systems. Also note that the operation of the spray nozzles is controlled by a number of additional sensors. Only at their signal, the electronic unit gives the command to inject fuel. As you can see, the scheme of the fuel system of the injector type differs from the carburettor one. First of all, it has separate injectors, which are engaged in fuel injection into the combustion chamber. Well and further, as well as in carburettor cars, the spark excites a spark and the cycle of combustion of fuel which then turns to a working stroke of the piston is carried out.

Diagram of diesel fuel system

The diesel fuel delivery system has its own characteristics. Firstly, the fuel supply to the combustion chamber is carried out by an injector under colossal pressure. Actually, due to this, ignition of the mixture in the cylinders takes place. On injector engines, the mixture lights up with a spark created by a spark plug. Secondly, the pressure inside the system forms a fuel pump (high-pressure fuel pump).

That is, the scheme of the fuel system (MAZ and KamAZ, among others) is such that two sprays are used for injection. One of them is low pressure, the second high. The first (it is also called pumping) carries out the supply of fuel from the tank, and the second one is directly engaged in injecting fuel into the injectors.

Below is a diagram of the fuel system (KamAZ 5320):

As you can see, it uses much more elements than carburetor cars. By the way, on some modifications of KamAZ engines an additional turbocharger is installed. The latter performs the function of reducing the level of toxicity of the exhaust gases and at the same time increases the total power of the ICE. Such a scheme of the fuel system (KamAZ 5320-5410) allows fuel to be pumped at a higher pressure. At the same time, the total fuel consumption remains at the same level.

Work algorithm

The principle of operation of diesel systems has many difficulties, in contrast to the injector. The scheme of the fuel system (Ford Transit TDI) is such that fuel with a boost pump passes through a fine filter and is fed to the injection pump. There, it comes under high pressure into the nozzles located in the cylinder head. At the right moment, the mechanism is opened, and after that, the fuel mixture is sprayed into the chamber into which the pre-cleaned air is fed through a separate valve. Excess part of the diesel fuel from the high-pressure pump and injectors is returned back to the tank (but not through the filter, but through separate channels - the tubes of low tide). Thus, the scheme of the fuel system of a diesel engine is more complex and requires a higher accuracy in the preparation of a combustible mixture. Accordingly, the maintenance costs for such engines are higher than for repair of injectors.

Conclusion

So, we found out how the scheme of the fuel system of a diesel engine and a gasoline looks. As you can see, the device of these nodes practically does not differ from each other, except for the type of fuel pumps. However, no matter what the scheme of the fuel system, the moment of preparation of a combustible mixture in modern cars is very small. Therefore, all mechanisms should work as reliably and smoothly as possible, because the slightest malfunction in their functionality can lead to uneven combustion of fuel and malfunctioning engine.