The correct approach is: position to pull the plunger to the top edges and corners with the plunger set flush into the center hole, slowly rotating the plunger, then there will be a sense block.

• 正确的处理方法是：将柱塞顶棱角部位拉至与柱塞套进油孔中心处平齐，缓缓转动柱塞，这时会有阻滞感。