Trouble phenomenon: A Dongfeng EQ1090D car has a muffler firing phenomenon during driving. During parking inspection, when the ignition coil high-voltage main line is unplugged, the ignition coil is tested at a distance of 34mm from the cylinder body, and the distributor is turned off or shaken. When the crankshaft was turned, the flashover was normal, but it was found that the power-off contact of the distributor was ablated. After grinding the contacts with sand bars and adjusting the gap to 0.35-0.45mm, the engine runs normally after starting, but when the car travels about 40 kilometers, the muffler fires again.
Exhaust ,Turbo manifold,Exhaust header,Tail Pipe,Exhaust catback,Exhaust muffler.
Fault inspection and troubleshooting: According to the above phenomenon, the cause of the muffler firing was carefully analyzed. In order to find the crux of the fault, the ignition sequence, the spring force of the distributor's power-off contact arm, the ignition timing, the spark plug, etc. were checked and no problems were found. Continue to check the carburetor air filter and valve clearance to no avail. I started the engine again and it worked normally, but it didn't take long for the old disease to recur.
Stop and check the distributor part again. Through disassembly and careful inspection, it was finally found that the copper glue wire from the contact arm of the breaker to the low-voltage terminal was broken at the corner, leaving only a few thin copper wires connected. After replacing the broken copper wire, the malfunction disappeared.
Fault analysis: When the copper wire of the low-voltage wire of the distributor is broken, the cross-sectional area of the wire is reduced, 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 it is more difficult to start, the engine can run normally after starting. After the engine temperature rises, the temperature of the ignition coil increases, and the resistance increases with the increase in temperature. Therefore, the high-voltage electricity generated by the ignition coil will be insufficient, the high-voltage spark will be weaker, and the fire will even be interrupted. As the fire is cut off from time to time, the combustible mixture that has not been ignited in the cylinder is discharged into the muffler. When it expands in the muffler, it will deflagrate when encountering sparks in the exhaust gas, which is manifested as the muffler firing.