How do I clear an air lock in the Danfoss pump on my Bentone Boiler?

I ran out of oil today (now re-filled) and when I hit the re-set button I hear the fan for about 10 secs but there's no ignition. The manual says this is probably an air lock but it doesn't say how to clear it. Can anybody give me some guidance please? The boiler is a Eurocal Consul. Thanks in advance