Throttle Body; Specifications; Functions And Construction - Subaru EX13 Service Manual

5. THROTTLE BODY

5-1 SPECIFICATIONS

This engine is equipped with electronic fuel injection .
The fuel system consists of a throttle body assembly, power generation module, wire harness,
crankcase air pulse hose, fuel pressure return pipe and a fine mesh fuel filter .
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, throttle position,
intake air temperature, and engine temperature to ensure proper engine performance .

5-2 FUNCTIONS AND CONSTRUCTION

5-2-1 FUEL PUMP
The fuel pump chamber is located below the throttle body .
The fuel pump is actuated by crankcase vacuum from the cylinder head nipple through the
crankcase air pulse hose, to a nipple located on the fuel pump .
The fuel flows from the tank into the fuel pump . When the fuel pump is actuated by the
crankcase vacuum, the fuel is pressurized by the pump and pushed into the throttle body
pressure port .
5-2-2 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 .
5-2-3 FUEL INJECTOR
The throttle body pressure port feeds fuel at a regulated pressure to the fuel injector .
Fuel is metered by the fuel injector that is actuated electronically by the Electronic Control Unit (ECU) .
The fuel is injected into the throttle bore and mixed with air from the air cleaner .
5-2-3 ELECTRONIC CONTROL UNIT (ECU)
The ECU (electronic control unit) on top of the throttle body is powered by the power generation
module when the engine is first rotated on start-up .
The ECU monitors engine conditions such as engine speed, throttle position, intake air
temperature, 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 .
The ECU also controls the low oil sensor system and monitors engine hours and other critical
engine data .
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