I done a job for a neighbour of mine Hammer, he had a derv van that kept cutting out, after a look around the fault was the Fuel seal in the filter, I replaced that job sorted, if you can, use a car power wash around the area of the pump & see if it is the pump. if you do decide Tony's route, mark the pump if you intend to remove the unit, on refitting don't use the Starter to prime, make sure the Fuel filter is full then hand primmer, make sure every Injector pipe is tight, + the inline fuel line.