Automotive Service Excellence (ASE) A8 Engine PerformanceIgnition System Diagnosis and RepairHard
A technician is performing a comprehensive inspection of an older vehicle's distributor-type ignition system. They notice significant corrosion and carbon tracking on the inside of the distributor cap and on the rotor tip. What is the MOST immediate consequence of this condition on the ignition system's performance?
- ACross-firing between cylinders.
- BIncreased spark plug gap.
- CReduced primary coil resistance.
- DPremature wear of the distributor shaft bushing.
Show answer & explanationAnswer & explanation
Correct answer: A. Cross-firing between cylinders.
Corrosion and carbon tracking on the distributor cap and rotor create alternative, lower-resistance paths for the high-voltage spark. Instead of jumping to the correct terminal, the spark can jump to an adjacent terminal, causing cross-firing between cylinders and leading to misfires or rough running.
Why the other options are wrong
- B. The spark plug gap is determined by the physical spacing of the electrodes and is not directly influenced by distributor cap condition.
- C. Primary coil resistance is an internal coil characteristic and is not directly affected by distributor cap corrosion.
- D. Excessive wear on the distributor shaft bushing would cause timing fluctuations or excessive play, not directly carbon tracking or cross-firing.
Distributor Cap Carbon Tracking
Carbon tracking and corrosion on a distributor cap create conductive paths that allow high-voltage spark to jump to incorrect terminals, leading to cross-firing between cylinders.
- Creates alternative spark paths.
- Causes spark to jump to wrong cylinder.
- Results in misfires and rough running.
- Visible as black lines or deposits.
Memory trick: Tracking makes sparks 'Cross Paths'.