yes a deisel tank is divided, as in it has a ection around the outlet, that makes it so that when you are low on deisel the outlet is always in the deisel so as not to pick up air, but i think that if you are half full then that should not occur, and if over half full then it certainly wouldnt happen, and i still cant see how it would make the engine race any way, but saying that im not saying it wouldnt, just that i would be surprised, there is no reason why you shouldnt give it some treater, i think forte is the best, and i would put it into a new fuel filter and put that on the van, that way you wont bring up any more sh t out of the tank, i suppose it could be veg oil use, but i dont think it would race again, but if it is veg oil damage then i would be looking at the pump, i dont have a lot of experience with lucas pumps so cant really say what reaction veg oil damage would do to it, but if you are not having trouble when the tank is full then it must be something to do with that. f i were you i would change the fuel filter put forte in the new one, and keep your tank fullish , rive it like that, if you dont have any problems then then i would either just top it up every 150 miles so never to get too low, if then after a few days or however often this has been happening before , you havent had a problem then its not what i suggested or the fuel pump. that will certainly wittle it down a bit as to the problem, but i wouldnt change anything apart from the filter until you have ruled them out
good luck anyway and dont forget to let us know how you go. i am away for 2 days tomorrow , so wont be able to assist, or hinder
you