starting problem Ford Focus Diesel 1.8

Very good, I have a Ford Focus that has brought me a friend and tells me the following: "My car started a few days ago to start and not start and I have changed the diesel filter, it still does not start, to make it loose the air entrance and I put directly to the collector, spray clean splashes at the same time that another person gives the start and so if it starts, lately I use gas. A great professional and I would like you to advise me if it can be for dirt, such as acting or influenced by using that diesel, also tells me that the breeding light was turned on and removed when the filter changed. I would thank you for advising me what to do, greetings

Good evening, you could send me some data such as the vehicle's vin or at least the year of manufacture, I do not know the type of fuel they use in their country, I suppose it is Spain, but we with only 10% of biodiesel have problems in Argentina.