Is this set new to you? Do you have experience with miitary generators? Did you read the TM (technical Manual)? Have you ever seen it running correctly? Does the oil pressure come up? You need to hold the switch in start for a few seconds after it is running until the interlocks are satisfied. I have a MEP 003a that has a slow oil pressure shutoff and I must hold it in start at least 15” after start—not normal but it works for that set. Try holding in start until the oil pressure stabilizes and the wait another 10” and see what happens—again, not necessarily normal but it may work. By the way, what are you doing with a 804? You understand it only produces 3 phase? I have two but I need it to run 3 phase equipment. You can finagle and get some single phase out of it but not what it was designed for.
Robert