Sequential Multi-port Fuel Injection (SFI)

WARNING: This page is about a different car, the 2007 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.

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 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 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 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.

Refer to FUEL SYSTEM - GENERAL INFORMATION article and FUEL TANK AND LINES article for additional information on the fuel pump, fuel tank, fuel tubes and the fuel filter.

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.

A constant fuel pressure drop is maintained across the fuel injectors by the fuel pressure regulator.

The fuel pressure regulator is attached to the fuel injection supply manifold and positioned downstream from the fuel injectors.
On a returnless fuel system, excess fuel supplied by the fuel pump, but not required by the engine, passes through the fuel pressure regulator located in the fuel tank. Excess fuel is diverted to the fuel tank.