Maybe Bob has shares in the photocell supply industry!!!!
Heres a few other possibilities.
1. Oil supply.
2. Motor
3. Pump
4. Control Box
5. Dog Drive
6. Solenoid
7. Blocked nozzle
8. Air supply
9. Electrodes
10. Combustion chamber problem (full of soot)
11. Good old photocell
Do yourself a favour, get an engineer in
jimtheboilerman, May 2012