This situation is usually caused by continuous injection of fuel by a certain cylinder injector of Bare Engine. Often before that, there will be difficulties in starting, idling jitter, black smoke from the exhaust pipe, and power reduction.

After disassembly and inspection, it can be judged by observing the combustion of each cylinder. Since the combustible mixture is richer than other cylinders, the cylinder and cylinder head will be darker than other cylinders. At the same time, the injector and its injection control circuit can be further checked.

The Mitsubishi Engine is bent or broken due to locking of the connecting rod and crankshaft. This situation is usually caused by poor lubrication of Bare Engine, which can be judged by checking the wear of the internal parts of the Mitsubishi Engine.

The problem of the connecting rod itself causes bending or breaking. This situation can generally be determined by analyzing the chemical composition of the connecting rod material, hardness testing, metallographic structure testing, and fracture analysis of scanning electron microscope.

The possible reason is that the quenching microcracks lead to low-stress fatigue fracture, and the mechanical properties and fatigue life of the connecting rod are reduced, including pearlite + flake, oversized non-metallic inclusions, blocky ferrite, etc.