What Causes Spark Leakage at the Crankshaft Pulley?
3 Answers
Crankshaft pulley sparking is caused by high-voltage electricity from the ignition system leaking to the crankshaft pulley, resulting in sparking. Below is an introduction to automotive part pulleys: 1. Pulley: A pulley, belonging to the category of hub-like components, is generally relatively large in size and is primarily manufactured through casting or forging processes. Larger-sized pulleys are typically designed for casting, with materials usually being cast iron (due to its good casting properties), while cast steel is rarely used (as steel has poor casting properties). Smaller-sized pulleys can be designed for forging, with steel as the material. Pulleys are mainly used for long-distance power transmission, such as in small diesel engine power output, agricultural vehicles, tractors, automobiles, mining machinery, machining equipment, textile machinery, packaging machinery, lathes, forging machines, power transmission for small-horsepower motorcycles, power transmission for agricultural machinery, air compressors, reducers, gearboxes, generators, cotton gins, etc. 2. Transmission Advantages: The advantages of pulley transmission include: the ability to mitigate load impacts; smooth operation with low noise and vibration; simple structure and easy adjustment; less stringent manufacturing and installation precision requirements compared to meshing transmissions; overload protection functionality; and a relatively large adjustable range for the center distance between two shafts.
I've been repairing cars for over a decade, and common cases of crankshaft pulley spark leakage usually occur due to surface wear of the pulley or aging and cracking of the insulation layer, which deteriorates its conductivity. High-voltage electricity, such as the current output from the generator, can easily leak from there, forming sparks. It could also be caused by insufficient or excessive belt tension leading to friction jumps, and accumulated oil or dust only makes matters worse. You need to check if the pulley is loose or cracked and test whether the voltage is stable. Safety first—don't mess around with it yourself; take it to a professional shop for disassembly and inspection immediately, or a minor issue could turn into a major engine overhaul. During regular maintenance, clean around the pulley to prevent dust buildup from affecting insulation.
Buddy, I've encountered similar issues when modifying cars. The crankshaft pulley arcing and leaking electricity is mostly due to the wheel being worn into pits or cracks, exposing metal parts that conduct electricity, combined with oil stains on the belt acting as a bridge, making arcing easy. It might be caused by loose installation or high generator voltage leading to leakage. I've learned my lesson—once, arcing burned out the wiring, costing me unnecessary money. I recommend regularly cleaning the wheel surface with a soft cloth, replacing low-quality parts, and adding an insulating sleeve as a precaution. If you see sparks, shut off the engine immediately and don't force it to run.
