In the interest of adding some personal experience to the forum, here's another post on progress with my bothersome boiler.
Changed the pump but the problem remained, in fact the boiler wouldn't light at all! so i carried out the following checks.
Started central heating demand, the...
Hi
My boiler keeps cutting out after about eight minutes on both central heating and hot water, the sequence seems to be;
Switch on boiler, demand hot water or central heating - Fan starts - igniter operates - boiler lights.
After eight minutes or so, flame cuts out - igniter starts - fan...