Fuel Charging and Controls

Sequential Multiport Fuel Injection (SFI)

WARNING: DO NOT SMOKE OR CARRY LIGHTED TOBACCO OR OPEN FLAME OF ANY TYPE WHEN WORKING ON OR NEAR ANY FUEL-RELATED COMPONENT. HIGHLY FLAMMABLE MIXTURES ARE ALWAYS PRESENT AND MAY BE IGNITED. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.

The Sequential Multiport Fuel Injection (SFI) system is classified as:
^ multi-point
^ pulse time
^ mass airflow

Fuel is metered into each intake port in a sequential firing order. Fuel injectors pulse to follow engine firing order in accordance with engine demand on a tuned intake manifold.

The basic fuel requirement of the engine is determined from the data supplied to the Powertrain Control Module (PCM) by the Mass Air Flow (MAF) sensor, which measures the amount of air being drawn into the engine.

Other sensors are used to measure:
^ air temperature
^ engine coolant temperature
^ engine speed
^ exhaust oxygen content

The various sensors detect any changes in the operating conditions and send signals to the powertrain control module. This permits the powertrain control module to control the opening duration (pulse width) of the fuel injectors and maintain optimum exhaust emission control and engine performance for all operating conditions.

Throttle Body
The throttle body:
^ controls throttle position by a conventional cable through throttle linkage.
^ controls air supply to the upper intake manifold by positioning the throttle plate.
^ is not adjustable.
^ cannot be cleaned.

Fuel Injectors
The fuel injector:
^ uses replaceable O-rings.
^ is electronically operated by the powertrain control module (PCM).
^ has an internal solenoid that opens a needle valve to inject fuel into the lower intake manifold.
^ atomizes the fuel as the fuel is delivered.
^ is deposit resistant.

Fuel Injection Supply Manifold

CAUTION: The fuel injectors and the fuel injection supply manifold must be handled with extreme care to prevent damage to sealing areas and sensitive fuel-metering orifices.

The fuel injection supply manifold:
^ receives fuel from the fuel supply line.
^ delivers fuel to the fuel injectors.

For removal and installation, refer to Fuel Injectors.