Fuel Charging and Controls
The Sequential Multiport Fuel Injection (SFI) system is classified as:^ multi-point
^ pulse-time
^ mass airflow controlled
Fuel is metered into each intake port in a sequential firing order. The system is controlled by the Powertrain Control Module (PCM).
The fuel delivery subsystem consists of:
^ fuel charging wiring harness
^ pressure relief valve
^ throttle body
^ fuel injection supply manifold
^ in-tank electric fuel level sensor and pump
^ a fuel filter
^ six fuel injectors
^ an in-tank pressure regulator
^ a fuel damper
Fuel Injection Timing
The period of time the fuel injectors are energized is control led by the PCM.
The pulse width is determined by the inputs from the:
^ Heated Oxygen Sensor (HO2S)
^ Mass Air Flow (MAF) sensor
^ Engine Coolant Temperature (ECT) sensor
^ camshaft synchronizer
^ Intake Air Temperature (IAT) sensor
Throttle Body
The throttle body controls the air flow to the engine through a butterfly valve. The throttle body includes:
^ a preset stop to locate the Wide Open Throttle (WOT)
^ a Throttle Position (TP) sensor.
^ the canister purge tap for evaporative emissions control
^ a sealant on the butterfly valve to reduce air flow when the throttle is closed (do not remove or clean sealant) and to reduce sludge buildup.
^ a closed throttle stop screw.
Fuel Injectors
The fuel injectors:
^ are electro-mechanical devices.
^ atomize and meter fuel.
^ are mounted on the intake manifold.
^ are positioned so the tips deliver fuel just before the intake valve.
^ are a solenoid-actuated valve assembly.
^ are activated by the powertrain control module.
Fuel Injection Supply Manifold
The fuel injection supply manifold delivers high-pressure fuel from the supply line to the six fuel injectors. The assembly consists of the following:
^ a connection for each fuel injector
^ a mounting flange for the fuel damper
^ a mounting port for a fuel injection supply manifold
Fuel Pressure Relief Valve
The fuel pressure relief valve:
^ is used to relieve fuel pressure.
^ is located on the fuel injection supply manifold.
Fuel Charging Wiring
The fuel charging wiring transfers electric signals to the fuel injectors. The signals from the powertrain control module determine the sequence and duration for the fuel injector firing.
Fuel Damper
The fuel damper reduces fluctuation of fuel pressure during injector operation.