by Russell Krick Publisher The Goodheart-Willcox Co., Inc Tinley Park, Illinois © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only (18 Topics) Gasoline injection fundamentals Gasoline injection classifications Throttle body and multiport injection Gasoline injection controls Electronic fuel injection Engine sensors Injector pulse width Throttle body injection Engine idle speed control Continuous throttle body injection Electronic multiport injection Air-fuel emulsion injector Unitized multiport injection Injector resistor pack Airflow sensing multiport EFI Pressure sensing multiport EFI Hydraulic-mechanical continuous injection system Fuel accumulator Uses pressure from an electric fuel pump to spray fuel into the engine’s intake manifold Provides the engine with the correct airfuel mixture for specific operating conditions © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Advantages Improved atomization Better fuel distribution Smoother idle Improved fuel economy Lower emissions Better cold-weather driveability Increased engine power Simpler © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Atmospheric Pressure Formed by the air surrounding the earth At sea level, the atmosphere exerts 14.7 psi (103 kPa) © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Vacuum Lower than atmospheric pressure Less than 14.7 psi (103 kPa) at sea level Sometimes called suction © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Differences in Pressure Cause Flow An engine uses differences in pressure to force fuel and air into its cylinders The engine acts as a vacuum pump, producing low pressure, or vacuum, in the intake manifold © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Set of low-ohm resistors Control current flow to each injector coil Protect windings from excess current Usually 5-7 ohms Often mounted in the engine compartment © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Injector Circuit Circuit contains resistor pack © Goodheart-Willcox Co., Inc Each pin corresponds to a resistor Permission granted to reproduce for educational use only Uses an airflow sensor as a main control Airflow sensor is placed at the inlet to the intake manifold Sensor converts airflow into an electrical signal for the computer © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Airflow-Sensing Multiport EFI © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Airflow Sensor Operation Throttle moved open for Throttle almost more power, increased flow closed, sensor pushes sensor flap open detects little airflow © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Uses intake manifold pressure (vacuum) as a primary control Pressure sensor is connected to the intake manifold Sensor converts changes in manifold pressure into changes in resistance Computer uses this data © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Pressure-Sensing Multiport EFI © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Continuous Injection System (CSI) Hydraulic-mechanical system Uses a mechanical airflow sensor to operate a hydraulic fuel distributor Continuous injectors spray fuel anytime the engine is running Continuous Injection System (CSI) Continuous Fuel Injector © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Cold Start Injector Extra fuel injector Sprays fuel into the intake plenum for cold engine starting and running Improves cold operation by enriching the air-fuel mixture Controlled by a thermo-time switch or control module © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Cold Start Injector © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Damps pressure pulses May maintain pressure when shut down to aid restarting © Goodheart-Willcox Co., Inc Permission granted to reproduce for educational use only Fuel Accumulator Components and Operation Engine running, fuel pressure compresses diaphragm spring © Goodheart-Willcox Co., Inc Engine off, spring pressure on diaphragm maintains system pressure Permission granted to reproduce for educational use only