The cycle of operation of the four-stoke engine begins with the piston at TDC and the intake valve open.
四冲程发动机的工作循环是以活塞在上止点、进气门打开为开始的。
The intake stroke starts with the pistonat the top of the cylinder (intake valve open and exhaust valve closed) and stops with the pistonat the bottom of its travel.
进气冲程在活塞位与气缸顶部（进气门开启，排气门关闭）时开始，在活塞到达其行程的底部时结束。
The intake valve was jammed open.
进气阀卡住了，关不上。
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