Started to cry when the engine conked out? (5,4)

I believe the answer is:

broke down

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'conked out?' is the definition.
('break down' can be a synonym of 'conk out')

I cannot understand how the rest of the clue works.

(Other definitions for broke down that I've seen before include "having stopped working" , "Became distressed" , "burst into tears" .)

I've seen this clue in the Evening Standard.

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