I know this is an old post but it is still very relevant today. My wife completetly turned the main valve off at the tank ??. All the advice given above is spot on, but just bear in mind the distance of the tank to the boiler. Mine is about 40m away and i therefore have 40m of air to get rid of before oil gets thro. It took me approx 15 to 20 bleed attempts before the boiler fired up....So dont dispair keep at it and it will work. Paul LLew
Paul LLewellyn, October 2022