Fuel Delivery and Air Induction: Description and Operation

Fuel System Components:

The function of the fuel metering system is to deliver the correct amount of fuel to the engine under all operating conditions. Fuel is delivered by the Throttle Body Injection (TBI) unit, which is controlled by the Engine Control Module (ECM), based on several important engine operation parameters. These parameters include engine speed, manifold pressure, coolant temperature, throttle postion, and exhaust oxygen content.

The main components of this system are the fuel tank, fuel pump, fuel filter, throttle body (including fuel injector, fuel pressure regulator and air valve), fuel feed pipe, fuel return pipe, air cleaner and ISC solenoid valve.

The fuel in the fuel tank is pumped up by the fuel pump, filtered by the fuel filter and fed under pressure to the injector installed in the throttle body. Fuel pressure applied to the fuel injector (the fuel pressure in the fuel feed pipe) is always kept a certain amount higher than the pressure in the intake manifold by the fuel pressure regulator. The fuel is injected into the throttle body in conic dispersion when the injector opens according to the injection signal from the ECM. The fuel pressure that is relieved by the pressure regulator is returned to the fuel tank through the fuel return pipe. The injected fuel is mixed with the air which has been filtered through the air cleaner in the throttle body. The air/fuel mixture is drawn through a clearance between throttle valve and bore and idle bypass passage into the intake manifold. Then the intake manifold distributes the air/fuel mixture to each combustion chamber.