Heating fires for 1min - 2min then flames cuts off. Does'nt lock out and pump keeps running. The boiler continually ycles like this. Flow pipe and pump get scalding hot but no heat on the return. Does the pump need replaced because the boiler does'nt seem to be getting rid of the heat?
If the HW works ok (you haven't specified), you can almost eliminate the pump. More likely problem would be the wax capsule in the diverter valve not opening correctly