I have a miller oil furance, was working fine until 2- days ago, looked as if there was no fuel coming out of tank, just had 150. Gal of fuel del about 3-weeks ago,at first opened bleeder air in lines some fuel not much blew lines out, some fuel not much, furance would not fire up, took gun out it was black I guess from fuel being pumped in jumped over the thermoset just to make sure it was not it, now seem like hardly any fuel coming out of tank, don't want to start replacing parts that don't need to be replaced any help, thanks