30/08/2025
Reading a spark plug 🔌 is a great way to check your engine’s health. Mechanics often “read” spark plugs to diagnose fuel mixture, ignition, and engine condition. Here’s a clear guide for you:-
🔧 Steps to Read Spark Plugs:
1. Remove the spark plug safely
-Let the engine cool.
-Use a spark plug socket to remove it.
-Don’t damage the insulator tip while removing.
2. Inspect the electrode & insulator
-Look closely at the center electrode, ground electrode, and porcelain insulator (the white part).
📖 Spark Plug Reading Guide:
✅ Normal Condition
Appearance: Light tan or gray deposits on insulator.
Meaning: Good air-fuel mixture, correct heat range, and healthy engine.
⚫ Carbon Fouled (Dry, Black, Sooty)
Appearance: Black, powdery deposits.
Cause: Rich fuel mixture, dirty air filter, excessive idling, weak ignition.
Fix: Check carburetor/fuel injection, clean air filter, check ignition system.
🟤 Oil Fouled (Wet, Oily)
Appearance: Shiny, wet oil deposits on plug.
Cause: Worn piston rings, valve seals, or cylinder wear (oil entering combustion chamber).
Fix: Engine repair needed, not just plugs.
🤍 Overheating (White, Blistered, Burnt)
Appearance: White, chalky insulator, blistered electrodes.
Cause: Lean fuel mixture, incorrect plug heat range, cooling issues.
Fix: Adjust fuel mixture, check cooling system, use correct plug type.
🟤 Ash Deposits
Appearance: Light brown/yellow crusty deposits.
Cause: Burning oil additives, poor fuel quality.
Fix: Try better quality oil/fuel.
🟢 Pre-Ignition/Detonation Damage
Appearance: Melted electrodes, cracked insulator.
Cause: Wrong fuel octane, timing too advanced, engine overheating.
Fix: Use proper octane fuel, check ignition timing, cooling.
