Guide To Your Vehicle's Fuel Injection System
10th February 2010
Guide To Your Vehicle’s Fuel Injection System
In 1990, the last model to roll out of the factory with a carburetor installed was the Subaru Justy. Since then, all cars have been designed with fuel injection systems (FIS). While carburetors were an impressive piece of machinery, they could not keep pace with the rapid evolution of automotive engines. Moreover, as emission standards rose, catalytic converters were installed into vehicles to reduce the harmful gases present in the exhaust. Because catalytic converters require a precise air-fuel mixture in order to do their job, the carburetor’s days were numbered.
Today, fuel injection systems carefully control the amount of gasoline that enters the combustion chamber of each cylinder. Below, you’ll learn how your vehicle’s FIS works and the process by which fuel is metered and controlled.
Basics Behind The System’s Operation
When you press down on your accelerator, a throttle valve opens and allows air to flow in toward the cylinders. Your vehicle’s computer (called the engine control unit, or ECU) takes note of the open throttle valve and sends fuel toward the injectors. This happens almost instantly to ensure the right air-fuel blend ends up inside the combustion chambers.
Each injector is a valve that opens to allow gasoline to shoot directly through the intake valve into its corresponding combustion chamber. It opens and closes quickly based on instructions received from the ECU. When the fuel flows through the injector, it comes out as a mist in order to burn more cleanly. The amount of fuel sent into the chamber is regulated by the amount of time the valve remains open. This period is called the pulse width.
How The Amount Of Gasoline Is Metered
Because the ECU is responsible for sending pulse width directions to the injectors, it must have a way to monitor the amount of fuel needed for specific driving conditions. It uses data from several sensors.
Oxygen sensors monitor the level of oxygen present in the exhaust coming from the combustion chambers. This data helps the engine control unit to identify a too-lean or too-rich mix and make the appropriate adjustments. An engine speed sensor is used by the ECU to regulate the injectors’ pulse width. A mass airflow sensor sends data to the ECU regarding the amount of air coming into the engine.
Other sensors monitor the throttle position, voltage level, operating temperature, and how much pressure exists in the intake manifold. All of this data is used to carefully meter the amount of fuel that flows through the injectors.
Your fuel injection system can develop a number of problems that will affect your engine’s performance. For example, your injectors can clog. Or, one or more sensors might fail, leading to a too-lean or too-rich air-fuel mix. These issues (and others) can cause a hard start, misfire, hesitation, or stall. If you notice any of these problems, visit a repair shop to have your car’s fuel injection system tested. Otherwise, you might eventually find yourself stranded at the side of the road.
No Comments »
No comments yet.
RSS feed for comments on this post. TrackBack URL