The pilots were so concerned, they never stopped the engines.

飞行员非常担心，他们从未停止引擎。

The ash got inside the engine, and suddenly the engine stopped.

灰烬进入发动机内部，发动机突然停止了。

On the other hand, lead was easy to extract and work, and almost embarrassingly profitable to produce industrially, and tetraethyl lead did indubitably stop engines from knocking.

另一方面，铅很容易提炼和开采，大规模生产极其有利可图，四乙铅确实可以防止发动机爆震。