Fuel Injector


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Do you want to know what an injector is and how this component works? Then read more about it here in our blog article.

What is a fuel injector?


The general task of the injector is to inject the calculated injection quantity of the engine control unit in every operating state of the engine (idle, partial load, full load).

Via the fuel pump, the fuel reaches the injectors in vehicles with direct injection. The engine control unit uses various parameters to calculate the exact amount of fuel to be injected by the injection nozzle.
The engine control unit sends electrical pulses directly to the injector valve, whereupon the injector valve opens so that the fuel can enter the combustion chamber.

As soon as the fuel has been injected, the fuel/air mixture is ignited and burned by the spark plugs.

Different types of injection

Single-point injection

Single Port Injection

Nowadays, single-point injection or “mono-motronic” is just a relic of the past. This is because, due to increasingly stringent emissions regulations, it is no longer possible for vehicle manufacturers to comply with the prescribed emissions standard with this type of injection.

With this type of injection, only one injector valve is used, which supplies all cylinders with fuel. Here the fuel pressure is about 1 bar. Also, this type of injection does not use a mass air flow sensor, but only a throttle potentiometer.

Multi-point injection

Multi Port Injection

With this type of injection, the injectors valves are usually located in the intake manifold. Here, as many injectors valves as the vehicle have cylinders are used (4 injectors valves are installed in a 4-cylinder engine).
Here, the air-fuel mixture mixes in front of the intake valves and then flows into the cylinder.
With this type of injection, the fuel pressure is up to 4 bar.

Direct injection


Nowadays, direct injection is probably the most common type of injection in new vehicles. For both diesel and gasoline vehicles.

Compared with intake manifold injection, the injectors (injection nozzle) are located directly in the combustion chamber. This means that the injector is not installed in the intake manifold but directly in the head of the engine.
With this type of injection, the fuel pressure can be up to 350 bar, depending on the manufacturer and vehicle model.

How to tell if fuel injector is bad?

A defective injector valve can lead to various problems in the vehicle’s fuel injection system:

  1. Irregular combustion or engine idling. If the injector can no longer work properly, an optimum air/fuel mixture is no longer available.
  2. Due to the significantly worse combustion, in most cases a defect of this component is also a loss of power of the engine noticeable.
  3. If the injector no longer works properly, the pollutants in the exhaust gas also increase. In the worst case, the exhaust emission test can no longer be passed.
  4. Illumination of the engine control light and various errors for this component in the error memory.

Injector leaking what can happen?

The first sign of a leaking injector is usually that the vehicle starts to jerk when driving and loses power.
It is also possible that the vehicle starts worse if fuel drips into the cylinder when the engine is switched off. This is because the spark plug cannot ignite this amount of fuel immediately when the engine is started, which means that not all cylinders run evenly in the first few seconds after the engine is started.

In the worst case, this can lead to oil dilution by the fuel. This can go so far as to cause the oil film in the engine’s cylinders to break down, which can result in engine damage due to excessive friction between the pistons.

How to test a fuel injector?

As already mentioned above, special attention should be paid to whether the vehicle jerks or loses power when accelerating or driving. Also, special attention should be paid to how the vehicle starts after a longer standstill. If the engine starts worse than usual or runs rough for a short time, this is an indication that an injector valve could be defective.

Also, of course, the fault memory should be read if there is a problem.

How much does it cost to replace a fuel injector?

In the case of fuel injection faults, it is very difficult to predict the cost of repair. The reason for this is that a complete component, e.g. an injection nozzle, can be defective, which can then quickly cost up to €500. However, the error can also be due to a defect in a cable connection, which is then much cheaper to repair.

For this reason, very thorough troubleshooting should be performed to avoid unnecessary costs.

How to use fuel injector cleaner?

Using an injector cleaner is not that difficult, but still you should follow the cleaner’s instructions.

  1. For most cleaners, the fuel tank should be completely full.
  2. Fill the cleaner completely into the fuel tank.
  3. Now you just have to start the engine and drive the vehicle. The best result can be achieved when the tank is emptied at once, such as on a trip on a vacation.

What is the best fuel injector cleaner?

As a rule, all injector cleaners work on the same principle, so here it is very difficult to say which is the best of all.

It should be ensured that the product comes from a well-known and reputable company.

Keep in mind, that every car has different software and modules built-in. Therefore specific features will vary with every model.

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