General Description

Fuel Control Schematic:

MULTI-PORT FUEL INJECTION (MFI)
The purpose of the fuel control system is to deliver the correct amount of fuel to the engine under all operating conditions. Fuel is delivered to the engine by individual fuel injectors mounted in the ports of the intake manifold.

The PCM controls the amount of fuel delivered by changing how long the fuel injectors are turned On and Off every 360 degrees of crankshaft revolution. This is called simultaneous double fire (SDF) injection.

The PCM uses one fuel injector driver circuit to control the fuel injectors. The current in this circuit is allowed to climb to a peak of eight amps, then is very quickly reduced to two amps to hold the injector open.

During closed loop operation, the main control sensor is the oxygen sensor, which is located in the exhaust manifold. This sensor indicates to the PCM how much oxygen is in the exhaust gas, and the PCM changes the fuel to the engine based on this information by controlling how long the fuel injectors are pulsed. The best mixture to minimize exhaust emissions is 14.7:1 air/fuel ratio, which allows the three way catalytic converter to operate most-efficiently. Because of the constant measuring and adjusting of the air/fuel ratio, the fuel injection system is called a Closed Loop system.

Simultaneous Double Fire (SDF) injection:

Fuel injector pulses are synchronized with the ignition reference (2X) pulse to the PCM. All fuel injectors are pulsed once each time that the number one cylinder is 60 degrees before top dead center (BTDC).