How to Determine the Condition by Spark Plug Color?
3 Answers
The normal color of a spark plug electrode is tan-white. If the electrode is burnt black and covered with carbon deposits, it indicates a malfunction. During inspection, you can connect the spark plug to the cylinder block, touch the central high-voltage wire to the spark plug terminal, then turn on the ignition switch and observe the high-voltage spark jump position. If the spark jumps at the spark plug gap, it means the spark plug is functioning well; otherwise, it needs to be replaced. Below are the spark plug conditions under different circumstances: 1. Normal spark plug: A normal spark plug is light brown. 2. Engine burning oil: Severe carbon deposits on the spark plug indicate that oil has entered the combustion chamber, commonly known as burning oil. Such a vehicle will emit thick blue smoke from the exhaust pipe. 3. Spark plug too wet: The heat value of the spark plug is too low or there is a fault in the electronic control system.
I've been driving trucks for twenty years, and checking the spark plug color is simple yet reveals major issues. During routine maintenance, I pull them out for a quick look: a tan color indicates normal combustion and a healthy engine; if it's pitch black, it could be a fuel system issue with excessive carbon buildup increasing fuel consumption; if it appears white or grayish-white, it suggests the air-fuel mixture is too lean or ignition is delayed, which can easily lead to engine overheating. Once on the highway, I experienced poor acceleration, checked the spark plugs to find them white, promptly pulled over to let the engine cool, and after replacing them, everything returned to normal. Oil stains or an orange-red color call for caution as they may indicate oil leakage. Remember, never ignore abnormal colors—seek professional repair early to prevent the fault from escalating and affecting driving safety.
As a car enthusiast, spark plug color is like a little magic mirror telling me the engine's condition. Checking it is simple: normal tan means OK, perfect combustion; black coating usually indicates too rich fuel mixture, carbon buildup causing power loss; white surface suggests too lean, prone to overheating damage; oily yellow may mean seal damage and oil leakage. I often check this when modifying cars, preventing major issues. Every time I change spark plugs myself, the car runs smoother and more fuel-efficient. Developing this habit is great—don't wait until a roadside breakdown to panic.
