Fuel Metering System

Purpose

The function of the fuel and air control system is to manage fuel and air delivery to each cylinder to optimize the performance and driveability of the engine under all driving conditions. Fuel is distributed through the fuel rail to eight injectors inside the intake manifold. Each port fuel injector is located directly above each cylinder's two intake valves. Fuel pressure is controlled by a pressure regulator mounted on the fuel rail. The throttle body regulates air flow from the air cleaner into the intake manifold, which then distributes this air to each cylinder's two intake valves. This allows the driver to control the air flow into the engine, which then controls the power output of the engine.


Components

The fuel metering system consists of the following parts:

^ The fuel supply components (fuel tank, pump, pipes).

^ The fuel pump electrical circuit.

^ The fuel rail assembly, including:

- The fuel pressure regulator assembly.

- The Idle Air Control (IAC) valve.

- The Throttle Position (TP) sensor

^ The Mass Air Flow (MAF) sensor


Basic System Operation

The fuel supply is stored in the fuel tank. The fuel sender allows retrieval of fuel from the tank and also provides information on fuel level. An electric fuel pump contained in the modular fuel sender pumps fuel through the fuel pipe and the fuel filter to the fuel rail. The pump is designed to provide fuel at a pressure above the regulated pressure needed by the injectors.

The fuel system in this vehicle is recirculating; this means that excess fuel that is not injected into the cylinders is sent back to the fuel tank by a separate fuel pipe. This removes air and vapors from the fuel as well as keeping the fuel cool during hot weather operation.