re diplomat adp8132, wont start wash, ?

When i switch machine on it makes the usual start up noises, filling etc, but does not start the cycle to wash. when it stops the 2 outside lights are on (not flashing, the soak & intensive. The last couple of times i used it, when it was washing during the cycle there was a explosion type sound, like air presure suddenly getting reased??. Any ideas please. thanks. Chris