I have had this with several cars - water under pressure squirts from the jets and then stops flowing - poking the jets with a needle or a piece of fine wire sometimes clears the obstruction but it lurks in the pipework and soon blocks up again.
It could be dirt but it's just as likely to be lime scale deposits from hard water - half a cup of Viakal in the water reservoir every year or so works for me.
It might work.
Good Luck..., November 2015
