we had this when it did ignite but kept going out it was due to the peasure guage. when using both hot water and the heating system we had to change the preasure guage from when we were just using the water in the summer. Not sure if this will help but have a look in your manual and see if the preasure gauge is reading the correct numbers!
sam
November 2008
Automatic Answer
We may have found other answers which could help you.