1996 GMC Yukon won't start

Have you checked the fuel pressure yet? should be around 40 to 50 psi. Is the check engine light on?

Thanks for the donation. A tune-up wouldn't hurt anything. Also, use a gage and check fuel pressure. Engine cranking, do you have spark at the plugs? You might try some injector cleaner, see if it helps?

If you don't have a fuel pressure gage, some of the national brand autostores used to loan out a fuel pressure gage. There are service bulletins about fuel poppets sticking, GM spider fuel system.