Full timer, you mention a pilot and igniter. Likely it isn’t both. Being a 93 I’d kinda expect a pilot but can’t say for certain.
As pointed out critters like to nest in the burner tube.
Since you’ve blown out the burner tube sounds like that’s not the issue. Just to be clear, the burner tube is where the heating flame goes, not where it comes from.
I’d suggest lighting it and watching for a few minutes. As pointed out, the flames (I’m assuming you have a pilot) should be a blue color.
The hard black stuff you mention may be soot which may be causing a problem.
Let us know what you find out.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks