The injectors: How they work and how to maintain them properly

Today we are going to talk about injectors, what they are, what their operation is, what problems they usually give us and how to prevent them.

As you will remember, the injection system serves to introduce high pressure fuel into the combustion chamber , just at the moment when the engine is in the compression cycle (in the top dead center).

When in contact with the air in high temperatures, it ignites causing combustion, in the case of diesel engines, and by means of the spark plug in gasoline engines. This system consists of a displacement pump capable of injecting different amounts of fuel and at different pressures , depending on the engine load, thanks to the internal pistons of the pump that are attached to each injector of the engine.

Therefore, given this, we observe that the injectors behave like solenoid valves capable of opening and closing an infinite number of times in a very precise way to the electric pulse that drives them; No leaks or fuel leaks.

These are the ones in charge of supplying the fuel to the intake duct or to the pre-combustion chamber, depending on whether it is a direct or indirect injection system respectively , in a pulverized way and without dripping so that the fuel is distributed in the most Homogeneous possible according to the engine operating regime, whenever we talk about diesel engines.

Now that we know what the injectors are, let's see what elements they have inside, explain how they work to understand it better. Each injector consists of a nozzle holder, nozzle, nozzle nut, cap nut, stem, fuel return connection, spring adjustment nut that keeps the injector needle closed whenever it is not injecting fuel and the fuel inlet.

How an injector works

It is simpler than it might seem in principle; Now we will explain it step by step to make it clear to you.

First of all, the fuel from the injection pump feeds the injector inlet. This fuel, which passes through perforated ducts in the body of the injector, makes its way to the needle located at the bottom that obstructs the exit hole when pushed through a rod by a spring. In this way the fuel cannot access the combustion chamber.

When the fuel pressure in the inlet duct increases sufficiently, thanks to the high pressure injection pump, the rod activates the spring of the injector needle, while the force with which the fuel will be sprayed is adjusted by of the nut that is linked to the same stem. The fuel circulates from the marked inlet to the perforated duct in the nozzle holder.

The tip of the needle valve, which is attached at the end of the nozzle, is responsible for preventing the passage of combustible liquid through the holes when it travels under pressure through the injector ducts. This needle will rise when you have to introduce the atomized fuel into the combustion chambers. In the process, a small amount of fuel is released upwards , allowing the needle, the nozzle and the rest of the components to be lubricated before leaving the connection for the return tube and returning to the tank.

The way in which the fuel is discharged we will call it an atomization pattern , and it will depend on the pressure it carries inside the injector as well as the number, size and angle of the holes in the nozzle since it is the last part responsible for injecting enough liquid charge into the combustion chamber so that it can burn optimally.

The nozzles, in detail

Now, depending on the type of engine and its size, we will find a wide diversity of nozzles . If we talk about engines with direct injection, we will find two types, according to the number of holes that contain:
  • Injectors with a needle diameter of 4 mm
  • Injectors with a needle diameter between 5 and mm

Note that at the moment the needle opens, the high pressure (400kg / cm2) acts inside the nozzle, to prevent fuel from passing through the gaps between the needle and the body of the nozzle.

These nozzles are manufactured with great precision , so much so that for the same batch of manufacture of these needles, it may be the case that they do not enter the body of others, or the same dust deposited on the needle can prevent it from sliding inside of the nozzle body. For this reason, when we have to work with injection nozzles, special care must be taken not to exchange parts and maintain a very clean environment.

But, applying some manufacturing processes of the nozzles where the tolerances applied in them are minimal for the parts that make up the nozzles, the fuel itself, with the passage of time and the millions of work cycles is slowly passing to the chamber that is found above the needle . It is a return line that returns that fuel to the inlet of the injection pump.

Injector Holes

Now that we have clear the operation of the injectors, we will move on to classify them. Before we have classified them according to the holes it has, either with 4 or 6 holes . We are going to make this new classification according to its operation, where we will find two types:

Mechanical injectors:

They were those of diesel engines until the arrival of single-rail or common-rail injection systems. They work by means of a system of feeding in charge to control the quantity and the moment to pulverize the fuel of mechanical form. They were also used at the beginning of injection in gasoline engines.

Electronic injectors:

They are the most used in gasoline engines. They have multiple sensors that send the information to the control unit so that it approves when and how much fuel must be provided at each moment. Therefore, the control unit activates them and they close by recovering an internal spring or spring. They are currently used in modern diesel engines, with multiple injections in each cycle.

Cleaning the nozzle holes

Already having clear some concepts of the injectors themselves, we will go on to comment on what are the most usual methods of cleaning them, since as we all know, the components of our cars are not eternal, although we can extend the operating time , as much as possible. For this we will only have to apply a good maintenance that includes a correct cleaning of them.

Therefore, the injectors, as we have explained above, are responsible for spraying the appropriate amount of fuel into the combustion chamber. Through them the fuel circulates continuously, being exposed to all the impurities that accumulate in the tank of the tank and end up passing to a greater or lesser extent to the fuel pump that is attached to the injectors.

If we are those who abuse the reserve or those who use poor quality fuel filters or simply take a long time to change them, for whatever reason, we have all the ballots so that we cause premature deterioration of the injectors by dirtying them in excess causing serious damage to the injection system and damage to our engine.

A little dirt in the injectors can cause us to pull on the accelerations or decelerations , but if we do nothing about it, the cylinder will stop working because of the obstruction of the injector, which leads to less power when canceling a cylinder.

If this happens, you will no longer be able to supply the engine with fuel, and we will notice that it does not work normally.

Injectors clogged: Symptoms

Before reaching this situation, we can see if our vehicle shows any of the following symptoms:
  • The injector may deliver less fuel due to obstruction or dirt.
  • The injector may have constant fuel leakage resulting in excessive consumption.
  • The injector may not have a correct spray pattern.
  • The injector may have several of the above problems.
  • If at any time we notice any of these 4 symptoms, it is time that we go to the workshop to carry out the corresponding maintenance, to prevent greater evils, which would lead to unnecessary repairs.
In addition to taking the necessary measures using preventive mechanics as we have told you, it is recommended that we clean the injectors every 100,000 kilometers for the first time approximately , and then every 50,000 km, so that we can extend the useful life by allowing them to operate correctly for longer.

Most common cleaning methods

Cleaning with additives

It consists of adding to the fuel tank cleaning liquids that uncover the injectors. It is the most economical and simple method to use, but not all vehicle manufacturers agree with its use since the aggressiveness of the chemical substances that they carry can damage the injectors in the long term.

Sweep cleaning

In this system a tank with the cleaning liquid is coupled to the vehicle. Once the system is connected, the engine is run so that the solution circulates on the fuel rail until the bottle runs out. When the cleaner is not diluted, it is more potent than the aforementioned additives, but due to the cleaning process, there is a greater risk of damaging the injectors.

Ultrasonic cleaning

With this method, we have to extract the injectors and place them in a test bench where they are washing and measuring different characteristics such as resistance, tightness, spray pattern and flow rate. It is the most effective method since it allows us to individually correct the possible defect of each injector. Of course, before reinstalling the injectors, both the seals and gaskets that are placed are new.

The biggest disadvantage, apart from the cost, is that you temporarily run out of the vehicle, since the injectors are removed and you have to send them to the laboratory.

Injector life

Like each and every one of the components of our car, if we know how to keep this system in good condition, it will not be necessary to replace it during the life of our vehicle.

The injectors, whether for diesel or gasoline engines, are essential components for the proper functioning of the engine of our vehicle , since they are responsible for dosing the exact amount of fuel that accesses the chamber, in addition to the main responsible for producing it adequate combustion

In principle, the vehicle injection system is made to last the entire life of the car , but both the mechanical and electrical parts of each injector are very complex and sensitive components, so that poor maintenance of this system can cause breakdowns. serious due to an accumulation of water in the reservoir, sediment debris, coming from the reservoir or a faulty spray;

These factors are going to be responsible for increasing fuel consumption, the level of CO2 emissions and even damaging the engine.

On the contrary, if the injection system is in good condition the spraying and dosing of the fuel will be optimal. In this way the engine will take advantage of its power, in addition it will work smoothly and without pulling, providing extra lubrication to the system, reducing consumption and emissions as well as helping to avoid the principles of oxidation since it removes water from the tank.

Tips to take care of your injection system:

  • Use chemical injector cleaning additives: Many fuel brands directly include a percentage of additives of this class in their fuel helping to eliminate impurities that can clog injectors.
  • Do not refuel during filling of suppliers: In theory, no gas station can sell fuel until that period has passed, but they do not always comply. Tank trucks recharge with power causing all the sediments stored in the dispenser to rise and can enter your fuel tank. So you know, if you see the truck refilled fuel tanks, do not refuel there, unless it is essential.
  • Do not rush the reservation of your vehicle: for the same reason as before, the grounds that are generated in the fuel tank are not convenient to reach the combustion chamber as they will force the pump and clog the injectors more easily.
  • Beware of biodiesel: these fuels absorb water and moisture and can accelerate the oxidation and corrosion of the components. Frequently they can present fungi or bacteria in the ducts, which can generate an obstruction and therefore deteriorate the injection system.
  • Change the fuel filter: it is responsible for keeping clean of impurities and retaining the water in the fuel. It is much cheaper to replace it periodically when it is dirty (at least every 30,000 kilometers) than to repair the injectors.
  • Control the revolutions: if we keep the engine below 2,000 rpm we generate more carbon, which will cause more vibrations and premature wear of the elements that form the injector system.
  • Clean the injectors: When we detect that they may be working improperly, according to everything we have told you, it is important that we go through our traditional workshop to be cleaned before the obstruction goes to greater.