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An electronic fuel injector is a precise and reliable component. Fuel injection is perhaps the greatest improvement made to modern automobiles. A fuel injector can regulate fuel flow within milliseconds. They do this for millions of cycles. Many people think such a precise device needs cleaning and maintenance. The truth may shock you.

How the fuel injector works

Parts of the basic electronic fuel injector

An electronic fuel injector works like an/off valve. Electrical current flows to one side of a magnetic coil. We control the ground side of the coil through the power control module or PCM. When needed, the PCM grounds the coil and it opens allowing fuel to flow. The PCM breaks the ground and it closes, stopping the flow of fuel.

The fuel control mechanism of the injector is the needle, often called a pintle and a seat. This is the actual valve component. A spring inside the injector pushes the pintle into the seat. A spring maintains the valve in a closed position until we need flow. 

Designers attach a permanent magnet to the shaft of the injector needle. An electromagnetic coil is just above the permanent magnet and mounted in the body of the injector. When the engine runs, we supply electrical current to one side of the electromagnetic coil. We connect the other side to a ground, through the power control module (PCM.)

Several sensors supply data to the PCM. These sensors tell the PCM when the cylinder will fire and how much air enters the engine. The computer also needs to know engine temperature and many other factors. The PCM calculates how much fuel we need. It precisely controls this by applying and releasing the ground to the fuel injector.

Applying a ground to the magnetic coil allows current to flow. Current flowing through the coil creates a strong magnetic field. The magnetic field attracts the permanent magnet. Magnetism overcomes the spring pressure and the pintle lifts off the seat. Fuel pressure sprays fuel through the injector until the current flow stops. When the PCM releases the ground, the fuel-injector spring closes the valve.

Controlling how much fuel

Fuel injectors in the open and closed positions


Engine combustion requires a precise fuel to air mixture. The ratio is 14.7 parts of air to fuel. When too much fuel is added, we say the engine is rich. A rich mixture does not burn efficiently. We lose power and fuel economy.

When the fuel/air ratio is less than 14.7 to one, we say the mixture is lean. Cylinder temperature rises and engine damage occurs with a lean mixture.

Flow-rate of an injector depends on its size and the pressure we apply to it. Fuel injectors do not vary their flow rate. The PCM controls the time the injector is open. The longer we hold the fuel injector open, the more fuel flows to the cylinder. When driving slowly, the injector may only stay open for milliseconds. At full power, the fuel injector may remain open constantly.

A cold engine requires a richer mixture to run properly. They design the PCM to keep the pintle off the seat much longer when the engine is below normal temperature. This is why a bad engine thermostat causes excessive fuel consumption.

Do we need to clean our fuel injectors?

Fuel injector flushing is not maintenance

They design fuel injectors to be self cleaning. Each time the injector closes, the pintle forces debris out of the seat. Gasoline contains detergents and the flow removes the debris. How much detergent varies in different brands of gasoline. Off brand fuel may only have the federally mandated minimum. Name brand fuel may contain far more detergent and other components to clean our injectors.

Because fuel injectors are self-cleaning, routinely adding fuel injection cleaner to the vehicle does no good. Too much cleaner can damage the fuel tank and the injectors. Fuel injection flushes, marketed as maintenance, are much the same. Injectors simply do not require routine cleaning. Instead, the client’s wallet is being cleaned with this wallet flush.

The electronic fuel injector is a marvel of engineering. Fuel injectors are dependable, reliable and need almost no service. The next time you hear "Flush your injectors," when you have no symptoms, just say no. Instead go to AGCO, we don’t work on cars, we fix them.

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