How Fuel Injectors Work

Here's how automotive fuel injectors work to distribute fuel into a car's engine.

Fuel injected vehicles have been around for the past 3 decades, largely replacing carburetor fuel injection. Fuel is injected into the air stream leading up to the cylinder (or in the cylinder itself) as opposed to being mixed in the barrel style carburetor upstream, and then getting sucked in as a air/fuel mixture.

Fuel injection allows an engine control computer to accurately measure how much fuel enters each individual cylinder, as opposed to controlling how much rich air enters all cylinders. It also can be scaled back for better fuel economy, or inject more for power, or skipped altogether for cylinder deactivation.

Today there are two types of fuel injection: port injected and direct injected engines. Port injection engines situate the fuel injector in the air intake so it mixes with the incoming air stream before the cylinder head valves. The rich air stream is then sucked into the combustion chamber and is controlled by the intake valve.

Direct injection engines situate the fuel injector inside the cylinder head itself, pointing into the combustion chamber. This allows fuel to mix inside the cylinder on its expansion and compression stroke.

In this video, a port injected engine is taken apart and the fuel system is examined, from the fuel rail, to the injectors, head and combustion chamber. A fuel injector is cut apart and examined, demonstrating the coil, plug connector, as well as the pintle valve and spray head.

The advantages of direct injection vs port injection are discussed, which includes better emissions, fuel economy and mixing. A demonstration on carbon buildup is also presented, with many modern engines offering both port and fuel injected engines to mitigate this issue, such as in Toyota's D4S system.

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[TheYesnoyesnoyesno]

Excellent - I love how you demystify these things without becoming either too theoretical or too specific. Thanks!

[AmrTX]

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[devonnewest]

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[F-Khan]

As always, precise, detailed and full of info. Hats off to you man.

[daaknait]

Very interesting and a clear explanation. I'm glad I'm not the only one giving a second life to used underpants.

[pchris]

When I googled this exact question I was expecting someone to just show the fuel injector itself and vaguely talk about it and not show what I was interested in which is _where_ the fuel is injected into the engine. I am quite fortunate to have found such an in-depth video that showed me everything I wanted to know and even some that I didn't know I wanted to know like the inside of the injectors. This combined with some good humor made for a very good video. RIP your brother lol

[oguzhanylmazer]

I just cant believe the engineering behind this. It happens multiple times a second and it is still nearly perfectly controlled. Just amazing.

[Conservator.]

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Tx for a excellent video!

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[FireguyNtx]

That was great, I been looking for a precise video of how they work, that's the one I needed. Thanks again for the good work.

[davidcardinal]

Currently becoming certified as a red seal ( YouTube) mechanic thanks to you!

[motoring]

Another great vid. Thanks for educating us man!

[anthonysmith]

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[spiritbuu]

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[DarkestHeartEvE]

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[feliped.koeniggonzalez]

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[Gunbudder]

it finally makes sense... best explanation i've seen of how exactly the injector works. most of the other things i read just said "it atomizes the fuel" but i could never find exactly how the fuel is shut on and off. the solenoid with a fail-close port is a genius way of doing it

[OCnStiggs]

Killer video. Concise. Very well spoken. (And quickly!) Great visual aids. Best on the Internet! The presenter again shows, he really knows his stuff!