Updated October 13th, 2016

Most of us have heard of the term "carburetor" before, but what exactly is it, and what does it do? For the uninitiated, the carburetor is a device that is designed to mix air and liquid fuel in an internal combustion engine. Along with providing this vital service, the carburetor also regulates the ratio of fuel to air in the engine, and it is tasked with controlling the speed of the engine.


How Does a Carburetor Mix Fuel and Air?


The carburetor benefits from the movement of the pistons inside their respective cylinders, which produces a type of vacuum action that draws air and fuel from the carburetor into the cylinders. The fuel-to-air ratio is controlled by a mechanism known as the venturi (a.k.a. choke). As air passes through the venturi, it increases in speed and air pressure drops, which sucks fuel into the air stream. The basic premise behind this feat of engineering is to burn fuel to create pressure, and then leverage that pressure to create motion. Remarkably, only a very small amount of gasoline is needed per combustion stroke in order to produce power for the engine; in fact, it only takes roughly 10 milligrams of fuel per stroke to get the job done.


Controlling Engine Speed


The carburetor contains a butterfly valve known as the throttle, which is opened whenever a driver presses down on the gas pedal. The wider the throttle is opened, the more fuel/air mixture is allowed into the engine, which in turn causes the engine to run faster. The converse is also true; if the throttle is barely open (e.g., the driver is barely pressing down on the gas pedal), very little air flow is created, which means that only a minuscule amount of fuel will be pulled into the engine.


A Constant Balancing Act


The carburetor's main job is to make sure that there is just the right mixture of fuel and air to enable the engine to run efficiently. If the mixture contains too little fuel, the engine will "run lean", which basically means inefficient performance, and could even lead to engine damage. If there is too much fuel in proportion to the amount of air in the mixture, the engine will "run rich", which can lead to problems such as flooding (which shuts it down), excessive smoke and sluggish performance.


This Summit Racing video will help explain further selections of Carburators and provide more details on how they work.



If your carburetor is giving you trouble and you're experiencing undesirable engine performance, you can always bring your vehicle to your local Virginia auto repair shop to so we can fix your carburetor problems Virginia style. You will have your carburetor examined and assessed by a certified Northern Virginia Mechanic, who will perform repairs or provide a replacement if need be.

Hogan & Sons can efficiently check all components of your vehicle as part of a vehicle tune-up. Visit our website at Hogan & Sons Tire and Auto has 8 locations throughout the Northern Virginia area including Sterling.

*Always check your owner’s manual for your vehicle model’s specific instructions before attempting any type of repair.