an air temperature sensor is used to provide the PCM with the temperature of the air entering the intake manifold.As the temperature increases, its resistance decreases the CTS is a temperature sensitive resistor (thermistor).the PCM can then inject more fuel the colder the engine is or less fuel as the engine warms up.a coolant temperature sensor (CTS) is used to provide the PCM with the temperature of the coolant.throttle position determines what portion of the 5 volt signal is at the PCM’s signal terminal PCM.

PCM can then adjust the quantity of fuel needed accordingly.

PCM interprets these return voltages as specific throttle positions.

A return signal is sent back to the PCM that corresponds with throttle position.

throttle position sensor (TPS) tells the PCM how much pressure the driver is putting on the throttle.

crankshaft position sensor (used on distributorless & direct ignition).

the distributor’s pick-up coil (vehicles with distributors) or….

engine speed, measured in RPM’s, is provided to the PCM by either….

these sensors provide engine information to the PCM….

How EFI Works Input Engine sensors ProcessingOutput Computer Fuel quantity Idle speed Spark timing Emission controls

3) Direct injection (newest design) injects the fuel directly into the combustion chamber.

intake manifold only delivers air so it can be designed for max.

more complex and costly compared to TBI.

delivers the fuel more precisely than TBI.

bģ main types of fuel injection… 2) Multi-port or multi-point injection (MPFI) not as common today (used a lot in the 1980s) fig.unequal fuel distribution with some condensation.

uses 1 or 2 injectors mounted on top of the throttle (fig.the computer turns on a fuel injector which sprays fuel, under pressure, into the intake manifold or directly into the cylinder.EFI uses a computer called a Powertrain Control Module (PCM) to decide how much fuel the engine needs.Electronic Fuel Injection during the late 1970’s and early 1980’s, government imposed minimum fuel mileage standards and tougher pollution control standards meant the end of the carburetor Electronic Fuel Injection (EFI), was developed to help manufacturers build vehicles that use less fuel, run cleaner and perform better

Fuel injection system ppt