How Does a Carburetor Cold Start Work?by Erik Arvidson
Vehicles that used carburetors for internal combustion struggled with starting or stalling in cold weather. It was because of hard starting in cold weather, and the need for cleaner emissions, that carburetors were replaced in the 1980s with computerized fuel-injection systems.
A carburetor blends vaporized fuel with a regulated amount of air for combustion in the engine's cylinders. Carburetors typically included a storage chamber for liquid fuel, an idling jet, a choke, an accelerator pump and an airflow restriction.
Most cold starting problems with engines using carburetors are tied to the choke, which is a valve at the top of the carburetor that controls the mixture of fuel and air delivered to the cylinders. When the engine is started, it needs a rich air/fuel mixture, and the choke reduces the air supply. The hard starting and stalling problems with carburetor vehicles in many cases was due to the choke sucking in too much air.
When fuel injection engines were introduced to replace carburetors, they were designed to solve cold starting problems by using a cold start injector, which would spray additional fuel into the intake manifold when the engine was started.