What are the two types of carburetors most commonly used on small reciprocating engines?

• A. Direct fuel injection.
• B. Float-type carburetors and pressure-type carburetors.
• C. Electronic fuel injection.
• D. Turbocharged carburetors.

Answer: (B)

The method of metering fuel in small reciprocating engines falls into two main types: float-type carburetors and pressure-type carburetors. Float-type carburetors use a float chamber that holds a reservoir of fuel; a needle valve keeps the fuel level steady, and as air moves through the venturi, fuel is drawn from the bowl into the airstream through jets, with throttle governing how much air (and thus fuel) flows. This classic design is simple and widely used on small engines.

Pressure-type carburetors meter fuel by maintaining a relatively constant fuel pressure in the metering system, using a diaphragm or similar mechanism to adjust fuel flow in response to air metering. They were developed to improve metering accuracy under varying conditions and are still found on some small engines.

The other options refer to fuel delivery methods that aren’t carburetors at all (direct or electronic injection) or don’t exist as a practical “carburetor” type (turbocharged carburetors). Therefore, float-type and pressure-type carburetors are the two most common carburetor types for small engines.