The bleeder screw is not a screw. :? It is a short nipple with a single hose barb on one end, a hex nut in the center, and a tapered seat (that you cannot see below the threads) in the body of the primer pump. It looks just like the bleeder fitting on a brake cylinder, and works the same way. I believe it is a 10 or 11 mm hex, best worked with a box wrench. Looking at the filter/primer assembly with the plunger on the right, it is located on the left side right under one of the hoses coming into the top section of the pump, opposite the pump push plunger. It is a little difficult to get the wrench on the hex. The outlet is a single rib barb and 1/8" clear vinyl tubing fits on it. I break it loose, then put the wrench on in a position that will get me at least a 1/4 turn, then push on the tubing, about 15" long, over the end of the bleeder. I drop the discharge end in a clear plastic bottle and start pumping. When you get the air out of the filter, you will get a steady flow into the bottle. Keep pumping until there are no bubbles in the fuel being discharged, then push the plunger once more and close the bleeder before you let off the plunger. With the bleeder screwed in tight, you should be able to pump to a hard plunger in very few strokes if the air is out. If you put fuel in the filter before installing it (this is NOT recommended by Cummins because it is unfiltered fuel) this goes much faster. Tip: tape the plastic bottle upright with masking tape to the step or the head door so it does not take off when you are pumping. A large rag under the filter is a good idea also since you may get a drip from around the bleeder threads.
