I have a 97 Grand Cherokee Laredo with a 4.0. The Jeep runs great, but if I drive it long enough for it to warm up. If I shut it off and go to start it again the fuel pump will not kick on when turn the key on. I can crank it over several times, and still nothing. If I leave it sit for awhile, 30 minutes or longer, get in and try to start it, the fuel pump will run and the Jeep starts fine. I can drive it without any problems, until I shut it off and go to start it again. I have replaced the fuel pump and the relay, check all the fuses and everything looks good. I need help, I do not know what else it cam be.