havin had probs with my maverick removed diesel filter was caked up in black slimey stuff bit like wet silicon put new filter on still no better replaced injectors still no better so put new diesel pump on now perfect so thought i would have a look in my old pump removed the top only to see the same caked inside pump black slimey stuff i reckon good clean and blow out old pump will be ok but the question is hows it got there when theres a diesel filter on and wot is the black slimey stuff any ideas ?????????