Fuel Delivery and Air Induction: Description and Operation
PURPOSEFuel Delivery
The fuel system supplies the fuel injectors with clean fuel at a controlled pressure throughout the entire RPM range and under all operating conditions. The system is called Sequential Fuel Injection (SFI).
Air Induction
The air induction system filters, controls, silences and delivers fresh air to the engine.
OPERATION
Fuel Delivery
The Fuel Pump (FP) is a Powertrain Control Module (PCM) output signal that is used to control the electric fuel pump. For electric fuel pump operation, the PCM grounds the FP circuit, which is connected to the coil of the FP relay. This energizes the coil and closes the contacts of the relay, sending battery voltage through the power-to-pump circuit to the electric FP.
High Speed Fuel Pump Operation
With the low speed fuel pump relay contacts in the normally closed position, full battery voltage is sent to the pump for high speed operation.
Low Speed Fuel Pump Operation
The PCM will ground the low fuel pump circuit, which opens the relay contacts. With the relay contacts open, power to the fuel pump must now pass through a "stand alone" resistor that is wired into the circuit.
When the ignition key is turned on, the electric fuel pump runs for about one second, but is then turned off by the PCM if a Profile Ignition Pick-up (PIP) signal is not received.
Air Induction
Air enters the system through the fresh air duct and flows through the air cleaner and is monitored by the Mass Air Flow (MAF) sensor. The metered air passes through the air duct and enters the throttle body. From the throttle body, the air passes through the intake plenum to the Intake Manifold Runner Control (IMRC) System.
The IMRC system has two intake manifold runners per cylinder for air flow into the combustion chamber. One runner is always open and the other is commanded open by the PCM. Below approximately 3000 rpm, the valve plates are closed and above approximately 3600 rpm, the valve plates are opened, to increase engine performance.