Sorry, but it's not like that at all. First of all, turbojets are continuous ignition engines: the combustion is continuous as long as the engine is running not intermittent, as it is in a reciprocating engine. And second, for startup and flight through heavy rain they use ignitors that are similar to sparkplugs on reciprocating gasoline engines. Once the engine is running above startup speed the ignitors are usually switched off.

The jet's combustion process is 'held' in one place by flame holders in the combustion chambers....kind of like a burner on a gas stove or furnace.

Anyway, jets only have compression ratios ranging from 3:1 to 13:1...not enough heat generated there to spontaneously ignite fuel introduced into a combustion chamber.
(http://www-psao.grc.nasa.gov/Reengine/types.html)

my .02

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