General System Description
SYSTEM OPERATIONThe 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.
COMPONENT OPERATION
Fuel Tank - The fuel supply is stored in a High Density Polyethylene (HDPE) fuel tank located in front of the rear wheels.
Fuel Sender - The fuel sender allows retrieval of fuel from the tank and also provides information on fuel level.
Fuel Pump - An electric fuel pump contained in the modular fuel sender pumps fuel through nylon pipes and an in-line fuel filter to the fuel rail. The pump is designed to provide fuel at a pressure above the regulated pressure needed by the injectors.
Fuel Rail - Fuel is then distributed through the fuel rail to eight injectors inside the intake manifold.
Pressure Regulator - Fuel pressure is controlled by a pressure regulator mounted on the fuel rail. 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 nylon pipe, This removes air and vapors from the fuel as well as keeping the fuel cool during hot weather operation.
Fuel Injector - Each port fuel injector is located directly above each cylinder's two intake valves.
Throttle Cable - An accelerator pedal in the passenger compartment is linked to a throttle valve in the throttle body by a cable.
Throttle Body - 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.
Fuel - Unleaded fuel must be used with all gasoline engines for proper emission control system operation. Using unleaded fuel will also minimize spark plug fouling and extend engine oil fife. Leaded fuel can damage the emission control system, and its use can result in loss of emission warranty coverage. All cars with gasoline engines are equipped with an Evaporative Emission Control (EVAP) system that minimizes the escape of fuel vapors to the atmosphere.
SEQUENTIAL FUEL INJECTION
The PCM controls the fuel injectors based on information it receives from several information sensors. Each injector is fired individually in engine firing order, which is called Sequential Fuel Injection. This allows precise fuel metering to each cylinder and improves driveability under all driving conditions.
SPEED DENSITY FUEL CONTROL
The PCM uses a Speed/Density model to calculate the fuel required to maintain an Air/Fuel ratio of 14.7 to 1. This ratio is the optimum ratio of air to fuel required for lowest exhaust emissions (called the stoichiometric ratio). The Speed/Density model looks at engine speed and air density (calculated from Manifold Absolute Pressure (MAP), Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) sensor information) to determine how much air is nowing into each cylinder. The PCM then calculates the length of time each injector must be turned on to provide the correct amount of fuel. This is called injector pulse width. The PCM looks at information from the 02 sensors to see if its injector pulse width is correct and makes adjustments as necessary.
SYSTEM COMPONENTS
^ Fuel tank
^ Fuel tank filler neck
^ Fuel filler cap
^ Modular fuel sender containing
- Fuel sender assembly
- Fuel pump
- Fuel strainer
- Fuel check valve
^ In-line fuel filter
^ Fuel and vapor pipes
^ Fuel pressure regulator
^ Fuel rail
^ Fuel injectors
^ Throttle body
^ Fuel pump relay
^ Powertrain Control Module and information sensors