Ignition System Diagnosis and Repair Flashcards
6 cards from real ASE4 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Ignition System Diagnosis and Repair flashcards as text
A technician finds a spark plug with a black, sooty deposit. This condition indicates:
Answer: A rich fuel mixture or oil fouling
Black sooty deposits on a spark plug indicate a rich fuel mixture or oil entering the combustion chamber.
An ignition coil primary resistance measures 0.5 ohms. The specification is 0.4–0.8 ohms. This means the coil is:
Answer: Within specification and serviceable
A primary resistance reading of 0.5 ohms falls within the 0.4–0.8 ohm specification, indicating the coil is serviceable.
A spark plug wire shows 10,000 ohms of resistance per foot. This is considered:
Answer: Too high — the wire should be replaced
Spark plug wire resistance should not exceed approximately 10,000–12,000 ohms total; 10,000 ohms per foot is excessively high.
An engine misfires only under heavy load. Spark plugs and wires test good. The NEXT most likely cause is:
Answer: Weak ignition coil output under high demand
An ignition coil that tests marginally at rest may fail to produce adequate spark energy under the high demand of heavy load.
What is the purpose of the secondary ignition system's high voltage?
Answer: To ionize the spark plug gap and initiate combustion
The secondary ignition system produces high voltage (20,000–40,000V) to ionize the gap at the spark plug and fire the air/fuel mixture.
When diagnosing a no-start condition, the technician confirms no spark at any cylinder. The FIRST component to check is:
Answer: The crankshaft position sensor
No spark at all cylinders points to a common input signal failure; the crankshaft position sensor is the most critical common trigger.