central heating problems

[holly]

Help my central heating has packed up!

My system is very old, the boiler is a "glow worm fuel saver F" and my heating programmer is a honeywell ST6300.

After turning the heating on all the radiators was working bar 1 down stairs so ive done the usual bleed the radiator, turned all radiators of upstairs but this still has failed.
So after turning the heating off and back on again manualy which caused a rumbling noise through the pipes? and now the boiler is not igniting at all have tryed igniting the boiler manualy as well.
The mid position valve is working fine and the motorised pump is working.

Any other suggestions? or new boiler ?

[AlBags]

I am assuming it is a gravity fed system fed from a small tank in the loft or above the HW cylinder.
Check the small tank is filling .. and the ballvalve/valve is not stuck off.
If there is no water, the system may be getting air into the primary circuit and not circulating water. The rumbling is usually pumped air.
Sounds like pump is trying to pump water and air.
Boiler willl not stay lit if HW cannot be pumped away. Check lockout system on boiler in this case.
Is mid-position receiving hot in the centre connector .. and passing to either port when selected HW, CH .. or both?
Pump should be whirring enough to hear it when switched on.