Fuel Delivery and Air Induction: Description and Operation

PURPOSE

Fuel Delivery

Fuel Delivery System:

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

Fuel Delivery System Schematic:

Variable Speed Pump
A two speed fuel pump control strategy is used to control fuel pump operation. The fuel pump receives either B(+) voltage high speed fuel pump or a voltage less than B(+) low speed fuel pump. The vehicle normally runs on the low speed fuel pump with the high speed fuel pump being activated during engine start up and high load conditions.

Low Speed Operation
The PCM grounds the fuel pump circuit. The Variable Load Control Module (VLCM) receives the request for low speed pump and activates the fuel pump output driver, sending voltage to the pump through the power-to-pump circuit. The power-to-pump circuit from the VLCM is designed so that the full B(+) voltage will not reach the pump.

High Speed Operation
The PCM grounds the fuel pump circuit and also sends a message requesting the high speed pump. With the fuel pump circuit grounded, the VLCM activates the fuel pump output driver as in the low speed operation. With the high speed pump requested, the VLCM will also ground its high fuel pump output circuit. This sends full B(+) voltage to the pump resulting in high speed operation.

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.