Check the injectors / injection nozzles? That's the process!

Thomas Wachsmuth September 20, 2023 Car repair & tuning guide

Injectors are components that significantly determine the combustion process in gasoline and diesel engines. If you suspect a faulty injection, it is advisable to check the injectors. But for the layman it is not easy based only on symptoms to see whether the Injectors are the cause. By the way, a professional inspection can just with special diagnostic devices take place. A car workshop is equipped with testers and can usually check the functionality of the injectors. The injection rates and engine running are monitored to detect any deviations or defects in an injector. The entire injection is a highly precise interaction and reacts sensitively to disruptions. In some cases it can be helpful, by the way sequence replace the injectors in the cylinders.

Checking the injector: root of the problem

There are a total of five different types of injection nozzles. For diesel engines there are three specific ones:

Pre-chamber and swirl chamber injectors are characteristic of older engines. These have mechanical control.
Modern diesel engines rely on this Common rail injection, which with violent pressures of up to to CE standards is working. The nozzles are activated electronically using a servo mechanism, whereby the injection can be split into 5 to 7 spurts.

And then there are the so-called Pump-nozzle systems, in which the nozzle is directly coupled to a pump, which in turn is positioned under the camshaft. The systems are electronically controlled. Volkswagen used the pump-nozzle principle, often abbreviated as PDE, in many diesel engines.

In diesel engines, the nozzles determine the start time of combustion. And no spark-generating component is necessary. Diesel ignites itself due to the high heat in the combustion chamber (Auto-ignition). When the engine is warm, the first drop of fuel immediately begins to burn. Since the amount of fuel is distributed over a certain period of time, the pressure increases steadily and ensures that the engine runs smoothly. This is an undesirable phenomenon in cold diesel engines Nail. At low temperatures, unburned diesel can accumulate in the combustion chamber as it evaporates with a delay due to the cold. This later leads to combustion, which experts call “Ignition delay" describe.

Two types of injectors for gasoline engines:

The majority of engines rely on injection into the intake pipe at a pressure of 3 to 5 bar.

However, there are also direct injection such as the FSI from Volkswagen or GDI from Mitsubishi. These systems operate at higher pressure because they inject directly into the combustion chamber.

During the injection phase and within the combustion chamber, a fine mixture of fuel and air forms. This combination is ignited by a spark plug, which is why the ignition process is called Spark ignition bezeichnet.

Inspect injectors: get to the root of the problem

An injector or injection valve has numerous fine openings, the size and number of which largely determine the injection pressure and the quality of the atomization. Over time, however, deposits from combustion can accumulate in the nozzle. Experts refer to the condition as “coking” and then often take one Nozzle control before. If the fuel is no longer atomized finely enough, combustion efficiency suffers and exhaust emissions increase. Diesel vehicles show the symptoms more often than petrol vehicles. It is therefore common practice for the diesel injectors in particular to be checked. With petrol engines it is often the case spark, which cause problems, less often the injectors. Special devices for injector testing help to find the defective cylinder.

Nozzle check: How experts find coked nozzles

If you would like to have the injection nozzles examined, the mechanic will first take all the nozzles out of the engine. Then he runs one for each injector Basic test to find possible problem areas. Below, the performance and spray pattern of each nozzle are checked in different operating conditions. The procedure is identical for diesel and gasoline engines. The most effective method of checking is a dedicated test bench, but only a few workshops have this.

Determining the spray pattern of the nozzle – how does it work?

In order to evaluate the spray pattern of a nozzle, there is special equipment on the test bench. For the test, the nozzle is securely attached and connected to a fuel supply. High pressure fuel is passed through the nozzle, revealing the spray pattern. An ideal pattern is always uniform. An uneven spray pattern indicates deposits that are interfering with fuel flow through the nozzle.

Injector problem – what to do?

If a check shows that the injectors are carbonized, there are various options available:

The most direct, but often most expensive, way is to install a new injector. This must then be adapted to the engine control using a diagnostic tool. A more cost-effective alternative is to use a replacement injector. Some also offer injector overhaul. The injector is dismantled and damaged parts are replaced.

Injectors – Why let the experts do it?

Work in modern diesel vehicles Common rail injection systems. The systems are almost inaccessible to the layperson. Not only are these sensitive, they also work under extremely high pressure, which can cause injuries if suddenly released. Various diagnostic instruments and tools are essential for interventions in the system. If the vehicle shows signs of engine problems, it is advisable to have the injectors checked - ideally by a professional.

What do the injectors & fuel injectors do?

The main function of injectors & fuel injectors is to either Petrol in the intake tract or diesel directly in the combustion chamber to distribute and atomize finely. You control the exact amount of fuel flowing through. There is usually an injection valve or an injector in each cylinder. If the injection occurs directly into the combustion chamber, it is a direct injection. The system is used on newer diesel vehicles and many gasoline engines. The nozzle valves open and close in fractions of a second. Technically speaking, the injector is a needle valve, with the needle resting on the seat of the valve. While in the past this worked mechanically, today an electronic control is usually used to direct the fuel into the cylinders. Ultimately, the injector ensures at the correct time the correct amount of fuel in the combustion chamber.

The following note is essential: For safety reasons, tuningblog recommends all repair, inspection and maintenance work exclusively to be carried out in a specialist workshop! Although our information is summarized to the best of our knowledge and belief, we cannot assume any liability for the content. All information is therefore "without guarantee".

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