A.incorrect electrode setting
B.incorrect nozzle position
C.clogged fuel nozzle
D.broken high tension lead

A.relight the boiler immediately to prevent loss of steam pressure
B.relight the fire off the brickwork as the bricks are cherry red
C.purge the furnace of any combustible gases before attempting to relight the fire
D.speed up the feed pump to prevent dry firing when the burner flame is reestablished