1996 Oldsmobile Bravada Sporadic Starting

Our 1996 Bravada has sporadic starting issues. It has happened twice. The first time (5 in the morning) it started right up and was driven approximately 1 mile to get gas. A half tank of gas was put in and it would not start. Had it towed home. At 5 pm, it started right up. No issues for one month. Then it sat outside for 12 hours and would not start at 5 in the morning again. No luck until 5pm that it evening, it started up and ran fine. Has ran fine for another month. When it won't start, we don't hear the fuel pump start. Any ideas if it could be anything other than the fuel pump?