Fuel guage problems

[amikk97]

I just replaced the fuel pump on my 87 r1500, I added about 3 gallons of gas to the empty tank, and the fuel gauge needle is showing as dead empty, however my truck starts and runs and I drove it around my yard for a minute. she still starts and runs, but the fuel gauge still says the same. I checked all the electrical connections and they all seem snug, do I just not have enough fuel in the tank for the float to pick it up? please help!