FAA Powerplant Written Practice Test

What is the fuel level within the float chamber of a properly adjusted float-type carburetor?

1. Higher than the discharge nozzle outlet

2. Equal to the discharge nozzle outlet

3. Slightly lower than the discharge nozzle outlet

4. Irrelevant to the discharge nozzle outlet

The correct answer is: Slightly lower than the discharge nozzle outlet

In a properly adjusted float-type carburetor, the fuel level in the float chamber is designed to be slightly lower than the discharge nozzle outlet. This design ensures that the carburetor maintains a proper balance for fuel flow into the engine. If the fuel level were equal to or higher than the discharge nozzle outlet, there would be a risk of flooding the carburetor, causing excessive fuel flow into the engine, potentially leading to engine performance issues or even engine failure. The slightly lower fuel level allows atmospheric pressure to help draw fuel up into the venturi of the carburetor during operation. This way, fuel can be atomized properly and mixed with air before entering the combustion chamber, optimizing combustion efficiency. The proper height ensures that the carburetor can effectively control the fuel-air mixture for a range of operating conditions without the risk of stalling or hesitation.