How Do Fuel Injectors Work?

Fuel injection systems have been standard on all cars for the last 19 years as the carburetor was phased out. So, just how do fuel injectors work?

The internal combustion engine needs three primary elements to function – air, gas and an electric spark. The elements of air and electric spark have always been fairly easy to control, but the gasoline element has not. The problem has always been efficiency. The carburetors of the “old days” provided tons of power, but burned fuel very inefficiently. Fuel injection systems are designed to address this problem.

Fuel injectors were first created as a method to create more control over the introduction of fuel to the piston chambers in the engine. The basic idea was to monitor the air pressure and other factors to determine just how much gas should be input to the intake chamber on each revolution. As computers have advanced, this process has become some complex that many new cars burn fuel at an efficiency rate of 95 percent. That’s astounding.

So, just how do fuel injectors work? The answer is fairly simply. Fuel is brought up from the gas tank using a fuel pump. It is run through a fuel filter and then up to a fuel rail. This runs across the top of the engine and sits over the fuel injectors. There are two primary types of fuel injection systems – multiport and sequential. Sequential is all the rage now, so we’ll focus on that one.

The sequential system is controlled by an engine control unit, better known as an ECU. It is fed information from a host of sensors in the engine. This allows the ECU to determine how much fuel should be introduced to each piston chamber before it fires to produce the maximum efficiency. The fuel is pumped from the fuel rail to the individual injectors and then into an intake chamber that sits just above the piston chamber. The air and fuel mix here and then are injected into the piston chamber at just the right moment.

The fuel injectors themselves look somewhat like a small spark plug. Fuel is introduced through the top of the injectors. It then passes through a small filter in the top of the injector. It then pools in a small compartment behind a plunger. The plunger is spring loaded. When the ECU is ready to introduce the fuel to the engine, it signals a solenoid to activate a spring. The spring pulls the plunger back and the fuel escapes around it. It then sprays out the end of the injector through the spray tip and into the intake area.

Modern fuel injection systems are very complex and very efficient. The ECU will take into account everything from the amount of air coming into the intake area to the weight carried by the vehicle to the weather outside. At their core, however, are the rather simple fuel injectors that make the entire system work.

<< Back to Fuel Injection