Ran out of oil the other day, had some delivered now but the boiler keeps cutting out after about a minute, then it will fire up again automatically after 10 seconds and then cut out again for another 10 seconds and so on. It is the Riello Burner, it has a red plastic removable cover, not sure of model number, sorry.
I was thinking maybe an airlock and if so how do I remove it.
Sounds like you need to clean the photocell, easy job! If that solves the problem, immediately check flue to ensure there's no black smoke, could be it will need a bit of a service, especially filters and nozzle change.