Fuel Charging and Controls

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.
- Fuel in the fuel system remains under high pressure, even when the engine is not running. Before working on or disconnecting any of the fuel tubes or fuel system components, the fuel system pressure must be relieved. Failure to follow these instructions can result in personal injury.

The sequential multiport fuel injection (SFI) system is classified as:
- multi-port.
- pulse width modulated.
- mass airflow controlled.

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 airflow (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 PCM. This permits the PCM 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 (TB):
- controls throttle position (TP) 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 injectors:
- use replaceable O-rings.
- are electronically operated by the powertrain control module (PCM).
- have an internal solenoid that opens a needle valve to inject fuel into the lower intake manifold.
- atomize the fuel as the fuel is delivered.
- are deposit resistant.

Fuel Rail

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

The fuel rail:
- receives fuel from the fuel supply tube.
- delivers fuel to the fuel injectors.