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or the 1995 model year, HarleyDavidson introduced electronic fuel injection for the first time on certain touring models. The Magneti-Marelli system that was introduced in 1995 saw use until the mid-2001 model year. In 2001 a new system, [Delphi], was introduced on EFI models and is still in use today. 2007 was the last year for carburetion on any HarleyDavidson motorcycle, and it was only available on certain models. This included the Sportster. The main difference in these systems is that while the Marelli system is a “return” style system while the later [Delphi] system is a “deadhead” system. For the purpose of this article, we will only gloss over the Marelli while we will do a deeper dive into the Delphi. For starters, we need to compare the similarities between these two types of systems. All HarleyDavidson’s with fuel injection features a fuel pump mounted in the tank. All HD EFI systems are sequential. (Sequential means that each cylinder
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DDecember ecember ‘21 - January ‘22 - CYCLE SOURCE MAGAZINE
Article & Photos By: Jason Hallman has its own dedicated fuel injector) carbureted model. On these models, and both systems require some type one check valve is for feed while the of pressure regulator to manage other is for return. Once the fuel pump the pressure on the inlet side of is initiated, the fuel in this system the fuel injectors. Also, both fuel stays in constant circulation. The injection systems have a throttle maintained pressure required on the body to manage the amount of air feed side of the system is regulated entering the engine and a dedicated by an external pressure regulator. ECM to control all functions relative The fuel that is not consumed by the to timing, fuel and monitor overall engine is simply “returned” to the engine performance. fuel tank, just like the name “ReturnLet’s now examine the differences Style” implies. between these two systems. As we mentioned, the Marelli system is a return system and was employed until mid-2001 on touring models only. The easiest way to identify these systems is by their dual fuel injection check valves on the left side of the tank, where you would normally find Pic 1: The Magneti Marelli system has two a fuel valve on the check valves. One feed and one return.
