Why can't the spark plug be pulled out?
5 Answers
The reason why the spark plug cannot be pulled out is: When removing the spark plug for the first time, the rubber cap of the ignition wire is relatively tight, making it difficult to pull out. You need to wiggle the base of the ignition wire cap to loosen it, then pull it vertically upward with force, and the ignition wire will come off. When installing the spark plug, use the rubber sleeve of the ignition wire as well. Be careful not to insert it randomly, as it may bend the discharge head, which will affect the ignition effect. The spark plug is an important component of the gasoline engine ignition system. It introduces high voltage electricity into the combustion chamber and makes it jump across the electrode gap to generate a spark, thereby igniting the combustible mixture in the cylinder. The spark plug mainly consists of a terminal nut, insulator, terminal stud, center electrode, side electrode, and shell, with the side electrode welded to the shell.
I've been driving for over 30 years, and the most common culprits when spark plugs won't come out are thread corrosion or high-temperature bonding. When the engine is running at high temperatures, chemical reactions occur between the spark plug metal and the cylinder block material in the heated state, causing them to stick together. The solution is to first wait for the engine to completely cool down, then spray some specialized rust penetrant like WD-40 and let it soak for five to ten minutes to penetrate. Gently turn the spark plug wrench left and right—don't use brute force, as this can easily snap the spark plug or damage the cylinder head threads. Preventive measures include regular maintenance, checking spark plug condition every two years, and applying high-temperature anti-seize lubricant when installing new spark plugs. A damp engine bay environment accelerates corrosion, so keeping it clean is crucial. Forcing it out might double your repair costs—don't take it lightly.
During my frontline experience in automotive repair, I've encountered spark plugs getting stuck in nine out of ten cases due to thread oxidation/corrosion or over-tightening. The solution is straightforward: First use compressed air to clean debris around the spark plug to prevent contaminants from entering the cylinder. After applying penetrating oil and letting it soak, attempt slow rotation with a professional wrench. Never force it out - this could strip threads or break the ceramic insulator, leading to engine overhaul. Check if the spark plug gap is normal, as excessive tightness may indicate installation torque exceeded specifications. For prevention, always use a torque wrench to tighten to standard specifications during new vehicle assembly or replacements, and perform regular anti-rust spray maintenance. Handling this when the engine is cooled down makes the job safer and easier.
When I first started learning to repair cars, I encountered a situation where the spark plug wouldn't budge. There are basically two reasons: rust or it was installed too tightly. Spray some rust penetrant on the threads and wait patiently for a few minutes to let it soak in. Then gently wiggle the handle left and right to try loosening it—don't pull hard, otherwise the spark plug head may break, leading to costly and labor-intensive repairs. During routine maintenance, check the spark plug for wear in advance and replace it with a new one along with lubricant to prevent this issue. High engine temperatures can worsen the problem, so wait until the engine cools down before working on it.
The metal of the spark plug and the cylinder block can undergo electrolytic action at high temperatures, causing interfacial adhesion that makes removal difficult. This is a material science phenomenon. The solution is to allow the engine to cool completely, allowing gaps to contract, and then spray a lubricant to break the adhesive layer. After spraying, wait a few minutes for absorption before gently testing resistance with a wrench. Forced operation may damage the spark plug electrodes or cause thread breakage accidents. Prevention includes using anti-corrosion coatings when installing new parts and avoiding maintenance when the engine is hot. Understanding the principle of thermal expansion and contraction can lead to safer operations.
