EETC EETC - Equipment & Engine Training Council Ignition Systems and Spark Technology Questions and Answers 2 — Questions and Answers
Question 1: An engine has good compression and fuel but will not start. A spark test shows a weak orange spark. What is the most likely cause?
- Clogged air filter
- Worn ignition coil or incorrect coil-to-flywheel air gap (Correct answer)
- Low engine oil level
- Dirty carburetor bowl
Correct answer: Worn ignition coil or incorrect coil-to-flywheel air gap
A weak orange spark indicates insufficient coil output, most commonly caused by a deteriorating ignition coil or an incorrect air gap between the coil armature and flywheel magnets.
Question 2: What does the kill switch (stop switch) on a small engine do to stop the engine?
- Cuts fuel flow to the carburetor
- Grounds the ignition coil primary circuit to prevent spark (Correct answer)
- Opens the throttle to cause a stall
- Disconnects the battery from the starter
Correct answer: Grounds the ignition coil primary circuit to prevent spark
The kill switch grounds the ignition coil's primary winding, which prevents the voltage collapse needed to produce a spark, stopping combustion and shutting the engine down.
Question 3: What symptom suggests ignition timing is too retarded (late) on a small engine?
- Engine knocks and detonates under load
- Engine lacks power, runs hot, and has difficulty starting (Correct answer)
- Engine runs smoothly at all speeds
- Engine overspeeds uncontrollably
Correct answer: Engine lacks power, runs hot, and has difficulty starting
Retarded ignition timing means combustion peaks too late in the power stroke, wasting energy as heat rather than pushing the piston, resulting in power loss and overheating.
Question 4: Which spark plug heat range should be used in high-load commercial equipment engines compared to light-duty residential equipment?
- Hotter plug in commercial engines to prevent fouling
- Colder plug in commercial engines to prevent pre-ignition under sustained high loads (Correct answer)
- Same heat range for all applications
- Heat range only matters for two-stroke engines
Correct answer: Colder plug in commercial engines to prevent pre-ignition under sustained high loads
A colder heat range plug transfers heat away from the tip faster, preventing pre-ignition in commercial engines that run under sustained heavy loads with higher combustion temperatures.
Question 5: What is the purpose of the resistor built into many modern spark plugs?
- Increase spark energy
- Suppress radio frequency interference (RFI) from the ignition system (Correct answer)
- Reduce required ignition coil voltage
- Prevent electrode wear
Correct answer: Suppress radio frequency interference (RFI) from the ignition system
The resistor inside the spark plug suppresses electromagnetic interference generated by the ignition spark, protecting electronic controls and nearby radio equipment.
Question 6: When inspecting a used spark plug with a white or gray blistered electrode, what does this indicate?
- Normal operation
- Engine running too lean or timing too advanced causing overheating (Correct answer)
- Excessive oil consumption
- Cold running conditions
Correct answer: Engine running too lean or timing too advanced causing overheating
A white or blistered electrode indicates the plug tip is running excessively hot due to a lean fuel mixture, over-advanced timing, or using a plug with too hot a heat range.
EETC EETC - Equipment & Engine Training Council Ignition Systems and Spark Technology Questions and Answers 2
An engine has good compression and fuel but will not start.
A spark test shows a weak orange spark.
What is the most likely cause?