Throttle Body; Specifications; Functions And Construction - Subaru EH72 FI Service Information

6. THROTTLE BODY

6-1 SPECIFICATIONS

This engine is equipped with Electronic Fuel Injection system (FI system) integrated with ECU
(Engine Control Unit) .
The FI system consists of throttle body (2-barrel), ECU, MAP (Manifold Air Pressure) sensor,
injector, pressure regulator, temperature sensor, electric fuel pump, and pulsation damper .
The fuel system is calibrated after careful testing for optimum all-round performance (including
starting, acceleration, fuel consumption, output power characteristics) .
The throttle body monitors air and engine temperature at start up and performs the choke
function automatically .
While the engine is in operation, the throttle body monitors engine speed, manifold air pressure,
and engine temperature to ensure proper engine performance .

6-2 FUNCTIONS AND CONSTRUCTION

6-2-1 ELECTRIC FUEL PUMP
The electric fuel pump is located below the throttle body, and actuated by power from the DC
battery . The fuel flows from the tank into the fuel pump . When the fuel pump is actuated by DC
battery, the fuel is pressurized by the pump and pushed into the throttle body pressure port .
6-2-2 FUEL PRESSURE REGULTOR
After the fuel pressure port is a diaphragm-type fuel pressure regulator .
The fuel pressure regulator relieves the throttle body of any excess fuel pressure and returns
excess fuel pressure back to the fuel tank through the fuel pressure return pipe .
6-2-3 FUEL INJECTOR
The throttle body pressure port feeds fuel at a regulated pressure to the fuel injectors .
Fuel is metered by the fuel injector that is actuated electronically by ECU .
The fuel is injected into the throttle bore and mixed with air from the air cleaner .
6-2-3 ENGINE CONTROL UNIT (ECU)
The ECU (engine control unit) on bottom of the throttle body is powered by DC battery . The
ECU monitors engine conditions such as engine speed, air pressure, and engine temperature .
With these inputs, the ECU actuates the fuel injector to ensure the fuel/air mixture is of optimum
concentration and is fed into the combustion chamber of the engine at the correct timing . When
engine speed reached to 4,200 rpm, the ECU cuts fuel to prevent over speed .
The ECU also controls the low oil sensor system and monitors voltage of DC battery, and each
wiring whether disconnecting or electrical short circuit .
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