Right i was coming down the motorway and the car just stalled

tryed turning it over and it just turned over but dont start i checked the cambelt and it was fine towed the car home put some petrol in primed the pump a few times and it started for about 5-10 seconds then cut out again tryed to start it a few times after that but nothing im thinking its a fuel problem as it did start then cut out or could it be a relay or something else anyone got any idears