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.
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 |
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.
For further information, refer to Fuel Supply Component Description for replacement procedures covering the fuel tank, fuel pump, fuel filter, and fuel pipes.
The accelerator control system is cable type (1). There are no linkage adjustments. Therefore, the specific cable for each application must be used.
When work has been performed on accelerator controls, always make sure that all components are installed correctly and that linkage and cables are not rubbing or binding in any manner. The throttle should operate freely without bind between full closed and wide open throttle.
When the ignition switch is turned to the On position (before engaging starter), the PCM energizes the fuel pump relay for two seconds, causing the fuel pump to pressurize the fuel system. If the PCM does not receive ignition reference pulses (engine cranking or running) within two seconds, it shuts Off the fuel pump relay, causing the fuel pump to stop.