To make sure that it is the diesel tube, apart from looking if you have any cracked or disconnected tube in the tank, you can place a tube from the diesel filter entrance to a carafe that you have with 5 liters of diesel on the ground.
In this way you are discarding the entire fuel line that you can not see, when you are prowned with the pear, the gasoleum should climb the tube, fill the filter and others, and if it does not go up it is that you have the diesel filter badly or that you have an air intake in the same filter.
So you save disassemble the deposit registration without being sure.
I have used this in a \ "Forito \" in an escort of the 98 that started, and the second stopped, (empty circuit) and no matter how much I looked and looked I did not see the diesel for any place until I realized that the diesel filter was touching my noses, air entered and the diesel returned to the tank when I was stopped for a long time.
Greetings (every teacher ...)