how can i fix my kangoo van 1.9 diesel?

when i start my van up from cold it runs ok but if i stop and start the van again it doesn't tick over and when i drive it there is a loss of power .it doesn't rev up and there is a miss on it i have been told it could be my injecter pump or my injecters can some one help thanks my van is 51 plate comman rail diesel its done 123 000 miles