Oil burner cuts out after a few mins. ?

I have an oil heater with a problem, it works fine for a few minutes, but then just cuts out. If I try to turn it on again, it doesn't work, but if I wait several hours and try again, again it works for a few minutes.

Another answer on this forum to what sounds like a similar problem is to check the pump as it may be over heating.

Is this the water pump? Hot water is coming through the pipe, and bleeding this pipe does cause hot water to come out. How do I check the pump? Is there anything else I should check? I've already cleaned the filter, and cleaned a load of rust out of the guts of the thing.

Thanks for any help!