AS9120B, ISO 9001:2015, AND FAA AC 0056B ACCREDITED

How A Fuel Injection System Works

In a fuel injection system, fuel is injected either directly into the engine cylinders or just ahead of the intake valve. The air intake for the fuel injection system is comparable to that utilized in a carburetor system, with an alternate air supply situated within the engine cowling. This source is regularly used when the external air source is obstructed and is usually operated automatically, with a backup manual system that can be utilized if the automatic feature malfunctions.

Basic Components of a Fuel Injection System

A fuel injection system generally incorporates six basic components: an engine-driven fuel pump, a fuel-air control unit, a fuel manifold (fuel distributor), discharge nozzles, an auxiliary fuel pump, and fuel pressure/flow indicators.

The auxiliary fuel pump provides the fuel-air control unit with pressurized fuel for engine starting and/or emergency use. After starting, the engine-driven fuel pump provides pressurized fuel from the fuel tank to the fuel-air control unit. This control unit replaces the carburetor and meters fuel according to the mixture control setting, sending it to the fuel manifold valve at a rate controlled by the throttle. Once inside the fuel manifold valve, the fuel is distributed to the individual fuel discharge nozzles. Located in each cylinder head, the discharge nozzles inject the fuel-air mixture directly into each cylinder intake port.

Why Are Carburetor Systems Being Replaced?

For years, internal combustion engines utilized carburetors to supply fuel to the engine. In fact, many other machines, including lawnmowers and chainsaws, still do. As automobiles and aircraft evolved, carburetors were no longer equipped to handle all of the operational requirements of such apparatuses. For example, to handle some complex tasks, carburetors have five different circuits: the main circuit, idle circuit, accelerator pump, power enrichment circuit, and choke. To meet additional requirements, catalytic converters were implemented. However, careful control of the air-to-fuel ratio was needed for the effectiveness of the converter. Despite such additions, carburetors were eventually replaced with throttle body injection systems first. Over time, new engines were designed and this system was quickly replaced by multi-port fuel injection. Similar to the fuel injection systems we are familiar with today, these systems have a fuel injector for each cylinder, usually positioned so that they spray directly at the intake valve. These systems provide more accurate fuel metering.  

Advantages and Disadvantages

A fuel injection system is considered to be less prone to icing than a traditional carburetor system. Nonetheless, impact icing on the air intake is still possible in either system. Impact icing usually happens when ice forms on the exterior of the aircraft and blocks openings, like the air intake for the injection system.

Some of the major advantages of a fuel injection system include reduction in evaporative icing, better fuel flow and distribution, faster throttle response, precise control of mixture, and easier cold weather starts. By contrast, some of the major disadvantages of fuel injection systems include difficulty in starting a hot engine, vapor locks during ground operations on hot days, and problems related to starting the engine that fails due to fuel starvation.

Conclusion

If you find yourself in need of fuel injection system components, such as air intake valves, fuel injectors, discharge nozzles, or other related items, like OAT gauges, engine cowlings, and more, rely on Automatize Industrials. Automatize Industrials in a premier distributor of top-quality aircraft parts, all of which have been sourced from top global manufacturers that we trust. Kickoff the procurement process by requesting a competitive quote on any desired item through our Instant RFQ service. For additional questions, call or email us at any time; we are available 24/7x365!


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