This unit is located in France where they use diesel not kerosene. The feed from the underground tank is not getting through to the boiler. The boiler works fine if I connect the hoses up to a remote tank of diesel. I am assuming that a filter is blocked somewhere but there is nothing between the boiler and the tank. On the top of the tank I can see the return pipe, the supply on/off lever and another pipe which I assume to be the inlet pipe. There is also a plastic bung in the centre which can be removed. I have pictures. My question is whether anyone knows if there might be a strainer or filter within the tank and if anyone has ever removed any of these components to clean them?