Firebird boiler will start up but stops & will nor restart

You may have a carbon build up on the ignition probes but this will normally cause a lock out. It may be that the circulating pump is faulty. Ie boiler fires up but due to no circulation it shuts down on the boiler stat and as the heat remains in the boiler it will not fire again until the heat has dissapated. Changing a circulating pp can be done by a confident DIYer but remember due to new legislation the old three speed pps are no longer available. You will need to purchase a modulating pump to match you existing pump. Old and new pump threads and spacing a are the same.