generally power is from valve head to pump+boiler, so if boiler is firing then pump should be getting power unless theres a break somewhere in feed to pump or something silly or maybe you have a wiring centre using a printed circuit board thats faulted????? need more info.....
you could have a gravity water and pumped heating where the roomstat isnt sending live to power pump so boiler just coming on to top up heat to water..... possibilities are endless,
more info req
ste, October 2009
