A Fuel injection system is more efficient than it's predecessor the carburetor
and can better operate at extreme temperatures while becoming more dependable at
start up. A fuel injection system reacts better to situations such as high altitudes,
extreme temperatures and variable fuel quality.
Fuel Injector
Fuel metering is determined by a combination of the engine air charge, vacuum
and speed. Some vehicles utilize a
mass
airflow sensor to determine engine air intake, other systems use a MAP sensor
(manifold absolute pressure)
Mass Air Flow Sensor
A throttle position sensor located near the throttle body, is used to measure
the load on the engine. The fuel system itself has the following components; fuel
pump, fuel pressure regulator, fuel lines, a fuel rail that the injectors are mounted
into and the injectors themselves.
Throttle Body
The fuel injector nozzle directs liquid fuel into the engines intake air stream.
The fuel system is controlled by a computer called a
Engine
Control Unit (ECU). The ECU controls the fuel injection system by gathering
and processing information from numerous sensors mounted into the system. There
are basic sensors used to determine the amount of fuel used, such as: coolant temperature
sensor, oxygen
sensor, air intake temperature, knock sensor, crankshaft angle sensor, camshaft
angle sensor and a
mass
air flow sensor. A fuel injector is normally closed and only opens when the
injector driver inside the ECM is commanded. The duration of this opening is called
the pulse width. An air charge is the amount of air inducted during each intake
event.
Common Problems and Fixes
Since most injection systems are computer based a simple hook up to a
diagnostic scanner will generally
let you know what the problem is. Simply replace the shorted sensor or repair the
vacuum leak. Then clear the trouble codes and recheck system. One hazard while servicing
a fuel injection system is the pressure involved. Use caution and slowly loosen
the fuel line to bleed off pressure.
Basic Maintenance
The main preventive maintenance you can do with a fuel injection system is to
keep your throttle body
clean. This is done by using any number of cleaner products.
How Does it Work
/ Fuel
Injection
Check Manufacturer Specific Fuel Injection
Questions and Answers
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