What Causes Unstable Engine Speed?

[VanCali]

The causes of unstable engine speed at high RPM include improper speed regulation adjustment, uneven fuel supply, or inconsistent fuel cut-off timing: 1. Improper speed regulation adjustment: Speed regulation rate is an important indicator for evaluating governor performance, representing the fluctuation degree of no-load speed relative to full-load speed at high RPM. If the regulation rate is too large, the diesel engine's speed fluctuation will be significant during load changes, affecting high-speed stability, and excessively high idle speed will increase engine wear. If the regulation rate is too small (indicating oversensitive high-speed control), it will cause unstable high-speed operation. 2. Uneven fuel supply or inconsistent fuel cut-off timing: When the engine reaches the cut-off speed, the fuel injection pump should automatically stop supplying fuel. However, if the plunger and delivery valve components have uneven quality or inconsistent wear leading to different cut-off timings, some cylinders may stop receiving fuel while others continue receiving small amounts or cut off slowly, all of which can cause unstable high-speed operation.