A fuel injection system is more efficient than its 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). Both utilize oxygen sensors to monitor
emissions in the exhaust to help control mixture.
Mass Air Flow Sensor
A throttle position sensor located on the throttle body, is used to measure
the load on the engine according to engine speed/vehicle speed/throttle position
and other information gathered by the computer.
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
Powertrain Control Module (PCM). The PCM 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 PCM commands it to. The duration of this opening
is called the pulse width.
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
Related Subjects
GET AN ONLINE
REPAIR MANUAL
FOR YOUR CAR. Get instant access to your vehicles drive belt routing, wiring
diagrams, trouble code information, updates and factory bulletins.
