FAA Powerplant Written Practice Test

What occurs if a magneto breaker point mainspring lacks sufficient tension?

1. The points will remain closed

2. The points will float or bounce

3. The ignition will be delayed

4. The magneto will stall

The correct answer is: The points will float or bounce

When the magneto breaker point mainspring lacks sufficient tension, the points do not close securely or may not close at all. This inadequate tension leads to a condition where the points can "float" or "bounce" instead of opening and closing cleanly in sync with the engine's operation. This bouncing effect occurs because there isn't enough spring force to hold the contact points firmly in place, allowing them to vibrate or oscillate when the magnetic field collapses. This results in poor ignition performance, as the timing of the spark becomes erratic, potentially leading to incomplete combustion. The bouncing of points can cause various issues, such as misfiring or inconsistent engine performance, because the ignition system relies on precise timing and stable operation of the breaker points to ignite the fuel-air mixture at the correct moment.