2.3 - System Configuration
Two fuel delivery systems are found on vehicles today:
01 - Return-type fuel delivery system
02 - Mechanical or Electronic Returnless fuel delivery system
The return-type model found on most EFI systems incorporate a fuel feed line, an in-line filter, a fuel injector rail, a pressure regulator and a return line. When powered, the pump supplies pressurized fuel to the injector rail. The fuel filter prevents contaminants from reaching the injectors. A regulator controls the pressure and returns excess fuel back to the tank via a return line.
The returnless fuel delivery type system made its appearance in the early 90's. The returnless system, by comparison, delivers fuel under pressure to the fuel injectors without the need of a return line. The regulator can be found in the fuel module assembly or externally mounted on the fuel tank or fuel feed line. The regulator is a constant pressure type which has no vacuum diaphragm.
