Fuel Charging and Controls

FUEL CHARGING AND CONTROLS

Sequential Multi-port Fuel Injection (SFI)

WARNING: Do not smoke, carry lighted tobacco or have an 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 serious personal injury.

The fuel charging and controls system includes the:
- throttle body (TB).
- fuel rail.
- fuel injectors.
- fuel pressure relief valve.

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

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

Fuel Injectors
The fuel injectors:
- use replaceable O-rings.
- are electronically operated by the PCM.
- have an internal solenoid that opens a needle valve, to inject fuel into the intake port in the cylinder head.
- atomize the fuel as the fuel is delivered.
- are deposit resistant.

Fuel Pressure Relief Valve
The fuel pressure relief valve is used to relieve fuel pressure from the fuel system and for diagnostic testing.

System Operation
The sequential multi-port fuel injection (SFI) system is classified as:
- multi-point.
- pulse time.
- mass air flow (MAF).
- fuel injection system.

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.

The basic fuel requirement of the engine is determined from the data supplied to the PCM by the 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.

The fuel injection supply manifold incorporates the electrically actuated fuel injectors directly above each of the engine intake ports. The fuel injectors, when energized, provide fuel into the intake air stream.