Fuel Injection Service
Fuel injection systems have been used in vehicles since the 1950's and widely used in cars made in Europe since around 1980. The last year a vehicle was produced in the United States without fuel injection was 1990 - the last vehicle using a carburetor. As emissions and fuel efficiency laws became stricter the fuel systems became more and more complicated. Operating requirements became so complicated that even all of the changes made to carburetors reached a point of being inefficient. Electric carburetors and single point and multi point fuel injection systems were then installed.
Catalytic converters were soon instituted as they monitor air-to-fuel ratios very well, provide excellent fuel metering and quick responses. In order to operate effectively it requires meticulous control of these ratios. Therefore oxygen sensors were added to monitor the amount of oxygen in fuel and exhaust.
An engine control unit (ECU) - a computer that controls all of the electronic components of the engine - was added to read the data from the sensors in order to adjust the air-to-fuel ratio among other tasks. The ECU is a very complicated component controlled by algorithms (formulas and tables) and software that enable the vehicle to satisfy the emissions requirements, meet EPA fuel economy requirements, and dozens of other requirements while also protecting the engine. The unit has performance chips that contain the tables with values that result in higher fuel ratings during specific driving conditions by supplying additional fuel or altering the spark timing.
In addition to oxygen sensors, the following sensors are controlled by the ECU:
Mass airflow sensor
Throttle position sensors
Coolant temperature sensors
Manifold absolute pressure sensor
Engine speed sensor
The complexity of these components make it imperative that your vehicle is worked on by highly qualified and trained professionals like we employee at Main Street Automotive Services.
The basics of how the fuel injection system operates
A vehicle's gas pedal is connected to a throttle valve that regulates the amount of air entering the engine. As the pedal is pressed the throttle opens letting in more air. The ECU ‘sees' the value open and increases the fuel in anticipation of more air coming into the engine. The air mass entering the engine is monitored by the sensors along with monitoring the amount of oxygen in the exhaust. The ECU fine tunes the delivery of the fuel so the rations are exact.
A fuel injector is a valve that is controlled electromagnetically receiving fuel under pressure from the fuel pump through pipes named fuel rails. The nozzle of the injector creates a fine mist of gasoline as a mist is more efficient than droplets. The time that the fuel injector remains open determines the amount of fuel supplied to the engine - this pulse width is controlled by the ECU. The injectors spray fuel directly into the intake valves as they are located inside the intake manifold. There are multi-port (injectors that open all at once) and sequential multi-port fuel injection systems (injectors that open just before the intake valve for its cylinder opens). The later responds quicker.