AMT Reciprocating Engine Ignition Systems 3 — Questions and Answers
Question 1: What does the term 'magneto timing' refer to in the context of reciprocating engine maintenance?
- The interval between magneto overhauls
- The relationship between when the breaker points open and piston position (Correct answer)
- The speed at which the magneto rotor turns
- The voltage output of the magneto at rated RPM
Correct answer: The relationship between when the breaker points open and piston position
Magneto timing establishes the crankshaft position (in degrees before TDC) at which the points open and the spark fires, directly affecting engine power and efficiency.
Question 2: Spark plug reach is defined as:
- The gap between the center and ground electrode
- The length of the threaded portion that protrudes into the combustion chamber (Correct answer)
- The overall length of the spark plug
- The distance from the seat to the terminal end
Correct answer: The length of the threaded portion that protrudes into the combustion chamber
Spark plug reach is the length of the threaded section; incorrect reach can cause the plug to sit too deep or protrude too far into the cylinder.
Question 3: A high-tension ignition harness that shows carbon tracking would most likely cause:
- A hot magneto that cannot be grounded
- Intermittent misfiring or cross-firing between cylinders (Correct answer)
- Higher than normal magneto output voltage
- Reduced breaker point gap requiring adjustment
Correct answer: Intermittent misfiring or cross-firing between cylinders
Carbon tracks provide a low-resistance path for high-voltage current to leak to ground or to adjacent leads, causing misfires or firing the wrong cylinder.
Question 4: When checking breaker point condition on a magneto, points that appear blue or burned indicate:
- Correct condenser operation and normal wear
- A faulty condenser allowing arcing across the points (Correct answer)
- Excessive spring tension on the breaker arm
- Too wide a breaker point gap
Correct answer: A faulty condenser allowing arcing across the points
A defective condenser fails to absorb the collapsing magnetic field energy, causing arcing at the breaker points that burns and erodes them.
Question 5: The distributor in a high-tension magneto system serves to:
- Step up the primary voltage to secondary voltage
- Route the high-voltage output to each spark plug in firing order (Correct answer)
- Regulate the timing of breaker point opening
- Store electrical energy for the next firing cycle
Correct answer: Route the high-voltage output to each spark plug in firing order
The distributor receives high-voltage pulses from the secondary coil and directs each pulse to the correct spark plug at the proper time in the firing sequence.
Question 6: Which of the following best describes a 'shower of sparks' ignition system?
- A system that fires all spark plugs simultaneously at startup
- An induction vibrator that produces a rapid series of sparks for starting (Correct answer)
- A magneto that increases spark energy by doubling coil windings
- Two magnetos wired in parallel to double spark intensity
Correct answer: An induction vibrator that produces a rapid series of sparks for starting
The shower-of-sparks system uses an induction vibrator to produce a rapid succession of sparks across the gap, making it easier to ignite the mixture during starting.
Question 7: What is the correct procedure if an engine continues to run after the ignition switch is turned to OFF?
- Immediately shut off the fuel and continue troubleshooting on the ground (Correct answer)
- Pull the mixture control to idle cutoff only
- Declare an emergency and land immediately
- Increase throttle to burn off residual fuel quickly
Correct answer: Immediately shut off the fuel and continue troubleshooting on the ground
A 'hot magneto' condition (broken or disconnected P-lead) means the magneto is not grounded; cutting fuel starves the engine safely while the fault is investigated on the ground.
AMT Reciprocating Engine Ignition Systems 3
What does the term 'magneto timing' refer to in the context of reciprocating engine maintenance?