Right guys , I have my car in a garage at the moment and it is being diagnosed for £150 . So far I have found at that the ACTUATOR wether it be electrical or vacuum has no relation to fault code P0251. After speaking to Ford specialist of 35 years on the phone (Truro vospers) it could be one of only 4 things . 1- Diesel injection pump attached to engine is knackered. 2- injectors one or more are failing 3- fuel rail incuding sensor 4 - The valve on the Diesel injection pump is faulty. I will update again later on . Good luck !