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.

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

The fuel charging and controls system consist of the following:

- Throttle Body (TB)
- Fuel rail
- Fuel injectors
- 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 fuel charging and controls system is:

- a Sequential Multi-Port Fuel Injection (SFI) system.
- pulse-width modulated.
- Mass Air Flow (MAF) 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.

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.
- Cylinder Head Temperature (CHT).
- 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.