Aircraft systems and instrumentsQuestion 647 of 934

What is the fuel primer used for?

  1. To increase fuel flow to the carburetor at cruise power
  2. To drain water and fuel from the carburetor bowl
  3. To reduce the engine temperature during a climb
  4. To vaporize fuel directly into the cylinders before starting
Show answer

Correct answer: To vaporize fuel directly into the cylinders before starting

It helps in cold weather, when there is not enough heat to vaporize the fuel in the carburetor.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Fuel Systems — Fuel Primer, page 185

Practice aircraft systems and instruments

Questions last reviewed: 18 October 2026