Philip Ralph t/a Boilerserv, 5, Marlpit Cottages, Heath Road, Boughton Monchelsea, Maidstone, Kent. ME17 4JN. Landline 01622 744040 or 01580 230328. Mobile 07774 432465. email: firstname.lastname@example.org.
Your oil tank itself may need servicing. This is more common in a steel tank than a plastic one.
Why service an oil tank?
When oil is delivered to the tank it is pumped from the oil tanker at a rate of 400-500 litres per minute, so, if the tank is close to empty, sludge which has built up over time in the tank can find itself being mixed with the oil, this sludge then ends up in the valve and or oil filter. Changing the filter gets you a clean filter but does not remove any blockage from the valve. The tank will need to be emptied, the valve cleared and the oil put back into the tank.
The picture to the left shows a blocked and sludged up tank fitting after the oil was pumped out and the tap removed, the picture to the right shows the sludge that was stopping the oil flow.
Steel tanks tend to have the outlet very near to the bottom of the tank whereas plastic tanks have the outlet 2-3 inches up from the base, this allows any sludge build up in the tank to stay away from the flow of oil. It is good practice to turn off any appliance when a delivery of oil is due (a vapourising cooker or stove will need to be cool before it's re-lighted)