1993 Oldsmobile Bravada Engine will crank but won't start.

It happened all of the sudden. But before this I noticed that sometimes I would have to double start the truck sometimes, meaning I would have to turn the engine over twice. But it always fired up on the second try. One day I have absolutely nothing but an engine that turns over. So I went ahead and bought some new plugs and wires(since I knew I needed them anyway) and installed them. I checked for spark and I have spark. Next I changed the fuel filter. To no avail. So I figured sometimes when I turn the ignition, the fuel pump didnt always come on. I figured I should check the relay. I looked into it a little and found that the pump doesn't turn on every time you turn the key in succession, as it is a time issue before it needs to reprime the fuel line(or so I read). It sounded reasonable to me. So I moved on to the fuel pump.I replaced it and the fuel sending unit due to a fuel line connection giving me problems. I went to start the truck and my battery was dead. So I replaced that as well, and after all that am back in the same position. A truck that cranks but will not fire up. Any help would be GREATLY APPRECIATED. Thanks