Do I need to prime the oil feed line?

We need help! Our oil furnace stopped running two days ago. I noticed the tank gauge down to the bottom of the tank, and I checked the tank and found it either very low or empty. We couldn't afford to fill the tank, so we only had the oil supplier put in 100 gallons. That was yesterday afternoon sometime. When I got home, the furnace would not start.
I opened the access door to the furnace, then loosened the feed line to the burner unit and discovered that there wasn't any oil in the feed line. The bobber in the sight gauge on the oil tank was resting at the bottom. I unscrewed the sight gauge and checked the bobber and found that it came up out of the oil, but when I let it go, it sank to the bottom indicating an empty tank. So now I see the bobber is not working any longer. There was oil in the tank, about 1/3 full.
I then loosened the top screw on the oil filter unit at the tank to find it dry. After about a minute, fuel oil started to appear in the hole, so I reinstalled and tightened the screw. The line runs through a pipe embedded in the basement floor and comes back out near the furnace. Shortly after coming out of the floor, the line goes to a 'T' fitting. I was only able to loosen the line coming from the furnace, and found fuel oil dripped past the threads, so I retightened that fitting. From the 'T' fitting the oil feed line goes up about 1.5 feet and then makes two loops then goes up about 6-inches and then passes through a hole on the furnace side about two feet above the floor. After opening all of the lines at those fittings, I re-loosened the fuel line at the burner unit and again found no fuel oil in that part of the fuel line.
Where do I go from here? Does the line need to be primed somehow? And if so, could someone explain how I do that?