A car muffler is a specialized device that obstructs sound transmission and allows airflow to pass through, preventing and controlling aerodynamic noise. Currently, in order to suppress environmental noise caused by high-pressure airflow emissions, there are various types of mufflers in the world, most of which use impedance composite silencing principles. However, due to complex structure, heavy weight, high-temperature oxidation sound absorption filler, Jet stream impact sound absorption filler, water vapor infiltration sound absorption filler and other reasons, muffler maintenance is frequent, noise elimination effect is poor, and service cycle is short, which has always been the main problem faced by automobile silencers.
Fault phenomenon: the silencer of a Dongfeng EQ1090D car was fired during driving. During the stop inspection, when the high-voltage main firing line of the ignition coil was unplugged, the fire was tested at 34mm away from the cylinder body, the power off contact of the Distributor was pulled or the crankshaft was cranked, the fire was normal, but the power off contact of the Distributor was found to be ablated. After sanding the contacts and adjusting the gap to 0.35-0.45mm, the engine started and ran normally. However, after the car had driven for about 40 kilometers, the muffler erupted again.
Fault inspection and troubleshooting: according to the above phenomenon, the causes of the silencer shooting were carefully analyzed. In order to find out the fault, the ignition sequence, the spring force of the power off contact arm of the Distributor, the ignition timing, and the spark plug were checked, and no problems were found. Continuing to check the carburetor air filter and valve clearance did not yield any results. Starting the engine again and running normally, but it wasn't long before the old disease recurred.
Stop the car and check the Distributor again. Through disassembly and careful inspection, it was finally discovered that the copper adhesive wire from the contact arm of the circuit breaker to the low-voltage terminal was broken at the bend, leaving only a few thin copper wires connected. After replacing the broken copper adhesive wire, the fault phenomenon disappeared.
Fault analysis: when some copper wires of the low-voltage conductor of the Distributor are broken, the cross-sectional area of the conductor decreases, which increases the resistance of the primary circuit and reduces the current in the circuit, resulting in insufficient high voltage generated by the ignition coil. When the engine temperature is low, although starting is more difficult, the engine can run normally after starting. After the engine temperature rises, the temperature of the ignition coil also increases, and the resistance increases with the temperature. Therefore, the high voltage generated by the ignition coil will be more insufficient, and the high-voltage spark will be weaker, or even cut off. Due to the constant interruption of the fire, the ignited combustible mixture in the cylinder is discharged into the muffler. When it expands in the muffler, it ignites when it encounters sparks in the exhaust gas, which is manifested as the muffler shooting.
