FAA Aviation Mechanic Powerplant (AMP)Ignition and Starting SystemsMedium
A technician performing magneto maintenance finds the breaker point gap set narrower than the manufacturer's specification. What effect will this have on ignition timing?
- AThere is no effect on timing, only a reduction in point service life
- BThe points open earlier than designed, advancing ignition timing beyond the E-gap position
- CThe magneto output voltage increases at all RPM regardless of point setting
- DThe points open later than designed, retarding ignition timing away from the E-gap position
Show answer & explanationAnswer & explanation
Correct answer: D. The points open later than designed, retarding ignition timing away from the E-gap position
The breaker point gap controls exactly when the points open relative to rotating magnet position. A narrow gap delays the opening point (points stay closed longer), moving the break away from the E-gap and retarding timing, which reduces spark energy and can cause hard starting or reduced power.
Why the other options are wrong
- A. Point gap directly affects timing, not just wear life.
- B. A narrow gap causes retard, not advance, of the opening point.
- C. Output voltage is affected by proper E-gap timing, not increased by an incorrect gap.
Breaker Point Gap & Timing
The breaker point gap sets the exact instant the points open relative to the rotating magnet, which must coincide with the E-gap position for maximum induced voltage.
- Set with a feeler gauge at maximum opening
- Too narrow = retarded timing (late opening)
- Too wide = advanced timing (early opening)
- Must align with E-gap for peak spark energy
Memory trick: Narrow gap = Nap late (retard); Wide gap = 'Way early' (advance).