in need some help! had a 1990 2.8 diesel for about a year now and never had any starting trouble it always fires instant. till today! went to start and it just went bluuuurrr like the battery was dead so i tryed to jump it didnt work just the same like the battery is flat so got me multimeter out bats got 12.8v so i checked heater plugs all but 1 working so i have replaced it and still no life in her can any help cause i just dont know!