Fuel Delivery and Air Induction: Description and Operation

PURPOSE

Fuel 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 Multi-Port fuel Injection (MFI) system.

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 (integrated in the PCM), This energizes the coil and closes the contacts of the relay, sending battery voltage through the power-to-pump circuit to the electric FP.

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.

Fuel Injection Timing
The PCM determines the needed fuel injector pulse width and outputs a command to the fuel injectors to meter the exact quantity of fuel. Each injector is energized once every other crankshaft revolution in sequence with engine firing order.

Fuel System Pressure
A constant fuel pressure drop is maintained across the fuel injectors by a fuel pressure regulator. The fuel pressure regulator is connected in series with fuel injectors and is positioned downstream from them. Excess fuel supplied by the fuel pump, but now required by the engine, passes through the fuel pressure regulator and returns to the fuel tank through a fuel return line.

PCM Malfunction
If at any time, the PCM malfunctions, or the battery voltage drops to an abnormal level, fuel injection will occur for all cylinders "simultaneously" once every two revolutions of the crankshaft.

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, where it is mixed with fuel for combustion.