I bought a 1997 gmc sierra 1500 with a 5.7L. After driving for 1.5 hours the motor just shuts off on me. I puled the fuel pump relay and plugged it back in and it started up and ran for another 5 to 10 mins and did the same thing again. I pulled the fuel pump relay and plugged it back in again and it started right back up and ran till it reaches idle and then dies out again. Had to have towed back to my house. This past weekend I went out and fired the truck up and let it sit for a couple of hours and it ran fine, till I drove it again for 1.5 hours and it did the same thing again. Any help with finding out what is wrong with it, would be greatly appreciated.