Section 03-04A: Fuel Charging and Controls—2.3L | 1993 Mustang Workshop Manual |
The MFI system can be subdivided into four distinct categories:
The fuel delivery sub-system consists of a high-pressure, electric fuel
pump (FP) 9H307, delivering fuel from the fuel tank to a fuel charging manifold
assembly.
A constant fuel pressure drop is maintained across the injector nozzles by a pressure regulator. The regulator is connected in series with the fuel injectors and is positioned downstream from them. Excess fuel supplied by the pump, but not required by the engine, passes through the regulator and returns to the fuel tank through a fuel return line.
Injectors 1, 4 and 2, 3 are energized in pairs, once every crankshaft revolution. The period of time that the injectors are energized (injector "on time" or pulse width) is controlled by the vehicle's powertrain control module (PCM). Input from various engine sensors is used to compute the required fuel flow rate necessary to maintain a prescribed air/fuel ratio for the given engine operation. The PCM determines the needed injector pulse width and outputs a command to the injector to meter the exact quantity of fuel.