I have a miller furnace

Question

I have a miller furnace with a becket burner. it is in a moble home and burn keroseen. My problem is I ran out of fuel and went to get more got 20 gal and put in tank. I have done this before and it started back up with no problem. This time it wont fire up and trips safty switch until i can reset. I have tried to manually bleed the two line system and it just seems like it wont get solid pressure. the motor dont sound like it usually does when I close the bleeder (usually sounds like a lugging motor) now it sounds like it is just running will not fire up. I do not see a filter anywhere is there one internal?
where can I find a detailed diagram of the whole essembly?