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SESK: Stuff Everyone Should Know · sesk.info/pilot-backfire-on-start

What is the main cause of backfiring when starting a piston airplane engine?

Opening the throttle too much after the engine fires.

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  1. Too much throttle after the engine fires ✔
  2. A low battery
  3. Leaving the fuel selector on both

Why: The AFH says excessive throttle after the engine fires is the principal cause of backfiring during starts. Moving the throttle slowly and smoothly, especially when the engine is cold, prevents it.

Huh, didn't know that: Right after any start, the next thing to check is the oil pressure gauge.

The dad joke
Why did the engine backfire? Someone gave it too much gas and it got a little cheeky.
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References

Answer: Too much throttle after the engine fires. The AFH says excessive throttle after the engine fires is the principal cause of backfiring during starts. Moving the throttle slowly and smoothly, especially when the engine is cold, prevents it.

  1. Airplane Flying Handbook FAA-H-8083-3C Chapter 2, Ground Operations www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/airplane_handbook/03_afh_ch2.pdf
    Excessive throttle opening after the engine has fired is the principal cause of backfiring during starting.
    Checked 2026-10-09.

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