Halliday & Matthiessen (1999: 538):
It might be maintained that a pair of expressions such as in times of engine failure and whenever an engine failed are simply synonymous, and do not imply any reconstruction of experience. But there are two problems with this view, One is that of history, referred to above. If neither had preceded the other, they could simply be free alternatives (though language is seldom so extravagant with its resources as this would imply!). But since one form of wording came first, it inevitably acquired a rich semantic loading. Since nouns evolved as names of classes of things, anything which is represented as a noun inevitably acquires the status of a thing, with the implication of a concrete object as the prototype. Thus in engine failure, the grammar has construed a thing called failure; and the nominal group then accommodates classes of failure (with another noun as Classifier), such as crop failure, heart failure and engine failure. Thus engine failure and engines fail are precisely not synonymous, because in engine failure the happening fail has acquired an additional semantic feature as the name of a class of things.