Ford Focus Service Manual: Fuel Charging and Controls

Sequential Multi-Port Fuel Injection (SFI)

The fuel charging and controls system consists of the:

• Throttle Body (TB) .
• fuel injectors.
• fuel rail.

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 on a tuned intake manifold.

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.

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 (TB)

The TB :

• controls air supply to the intake manifold by electronically positioning the throttle plate.
• is not adjustable.

Fuel Injectors

The fuel injectors:

• are electronically operated by the PCM.
• atomize the fuel as the fuel is delivered.
• each have an internal solenoid that opens a needle valve, which injects fuel into the intake port in the cylinder head.
• are deposit resistant.

Fuel Rail

The fuel rail:

• receives fuel from the fuel supply tube.
• delivers fuel to the fuel injectors.