you should have mentioned boiler knocking badly after new pump fitted
nevermind
check pump valves are open
check power to pump
check system bled & vented
AWOL
June 2012
thats what we thought and fitted a new pump
jim
June 2012
defective pump
AWOL
June 2012
I can answer this question...
my Glow-worm fuelsaver mk2 fires up knocks badly and then closes down what do?