Engine Mechanical problem
1999 GMC Sonoma 6 cyl Two Wheel Drive Automatic 106000 miles

I was driving home and all of a sudden, my truck stalled and I was forced to coast into a parking lot. I tried starting the truck again, but it would not turn over. The engine cranks, but does not start. I still have a full charge on my battery, and my alternator passed a diagnostic, because that's what I thought it was. I checked the relays and fuse panel under the hood and everything is ok. I was having a problem with my gas gauge, where it was reading empty when I was stopped, but the tank was full. I'm not sure if it's the fuel pump or a problem with the electrical system. Any help would be greatly appreciated!