The small fuel line between the primer and fuel tank is empty, if it's anything like my Tundra, it actually Tee's into the supply line for the fuel pump. Cranking the engine over with the electric start will cycle the pump and pull fuel into that line, which can then be drawn up the smaller line into the primer housing. My Tundra has the same problem at the start of the season, I just un-hook the inlet line from the back of the primer and gently siphon fuel up the line with my mouth. Re-attach it to the back of the primer and you're good to go.