In message , Fentoozler
writes

Does this boiler have a fan and is it running when the ignitor is
"clicking"? Some boilers require a pressure difference to turn on the
main
burner but this condition may also apply to the pilot.

The "CF" (conventionally flued) indicated to me that it was not fan flued


Just a thought.



--
geoff

Plus the OP said he was getting 'sparking' at the pilot, this wouldn't
happen until a fan had proved any air pressure switch.

Yes - conflicting info to my mind.

Really the OP needs to say whether it's got an electronic control or not
(part No 407779 - a black module about 3" x 6" which stands on four
legs)


--
geoff