FAA Powerplant Written Practice Test

When a new carburetor is installed on an engine, what should be done first?

1. Adjust the idle speed

2. Warm the engine up to normal temperatures

3. Check the fuel pressure

4. Recalibrate the ignition timing

The correct answer is: Warm the engine up to normal temperatures

When installing a new carburetor on an engine, the first step should be to warm the engine up to normal temperatures. This is crucial because the carburetor's performance can be significantly affected by engine temperature. When the engine is at operating temperature, the various components within the carburetor can expand to their proper dimensions and the fuel mixture can vaporize effectively, allowing for a more accurate and consistent fuel-air mixture. Performing adjustments, such as idle speed or ignition timing, is most effective when the engine is warm, as these settings can vary when the engine is cold. Additionally, checking the fuel pressure is also best done when the engine is operating normally to ensure that the carburetor is delivering fuel at the correct pressure under typical operating conditions. Thus, warming the engine first is a vital step in ensuring optimal performance and accurate adjustments for the new carburetor installation.