How Do I Get Oil Into Burner?

Oil ran out,had some delivered last week,tank now half full but burner won't light.Pipework from tank in garden comes straight up vertical through kitchen floor,then a straight section,then pipework goes into boiler housing and up,round and connects into pump of burner.I think oil stuck just outside house - is this the same as an airlock?Burner is Riello RDB1.I've undone small allen screw on side of pump but no oil or bubbling.Have also disconnected flexible supply pipe from pump and put it in bowl but no oil came out.Have not tried black nut with rivet sticking out the middle and have not tried long brass hexagon-shaped part 3 inches long with allen screw on the end as I think these are both something to do with the oil pressure and initial settings of boiler.Please does anyone know what I should do?I can mend most things but this is defeating me! Thanks, Emma