I think water may of got into the system.
The tank ran completely out and i noticed as i was bleeding it that there was residual amounts of water coming through the bleed nosel. I keep bleeding it into a bucket until i thought it was all gone. On firing up of the boiler i had no problems and it fired up and was working for a number of hours. It now keeps locking out and even when i try bleeding it off there is nothing coming out. the sound i am hearing when i press the red button is not the normal tone, it is going through the motions yet the noise seems duller and when it trys to fire up it just locks out. There is oil there at the boiler as i sucked on the bleed nosel and got a mouth full, though the pump will not pump it through so it just keeps locking out. Is there anything i can do or is this one for an experts?

Nicky, February 2013