Have just remove the gl and filter from my efr 40 single fuel line oil boiler and now it wont fire up.?

This boiler was working fine until i decided to remoe the oil gl and filter to clean them.I filled up the gl and the 2 pipes leading to the pump but after around 20 seconds the motor cuts out so , ume i have created an air lock which needs bleeding.This sytsem has only one pipe coming from the fuel tank which has 2000 litres of fuel in it.HELP !!!!