Fuel Control Operation - Fuel Injected Models

An in-tank electric fuel pump delivers fuel to injector(s) through an in-line fuel filter. The pump is designed to supply fuel pressure in excess of vehicle requirements. A pressure regulator mounted in fuel rail (port systems) or throttle body unit (throttle body systems) keeps fuel available to injectors at a constant pressure of 9-13 psi (.6-.9 kg/cm² ) at idle for throttle body injection and 30-43 psi (2.1-3.0 kg/cm² ) at idle for port injection systems. Excess fuel is returned to fuel tank through pressure regulator return line. For fuel system performance check, see appropriate CHART A7, FUEL SYSTEM DIAGNOSIS for that specific system.

• Throttle Body Injection (TBI) - An electrically pulsed injector is located in intake manifold throttle body unit. The ECM controls injector "on" time (pulse width) to provide proper amount of fuel to engine. The 5.0L (VIN E) and 5.7L (VIN 7) engines use a throttle body with 2 injectors.
• Port Fuel Injection (PFI) - Individual, electrically pulsed injectors are located in intake manifold. These injectors are next to intake valves in cylinder head. The ECM controls the "on" time (pulse width) of each injector to provide the proper amount of fuel to engine. Standard PFI systems feature simultaneously double-fired injection. On these systems, all injectors pulse one time for each engine revolution. Thus, 2 injections of fuel are mixed with incoming air to produce the fuel charge for each combustion cycle. On models with Sequential Fuel Injection (SFI), injectors are pulsed sequentially in spark plug firing order.