1997 Suburban 7.4 4X4. This is my fiancee's truck and we are having problems starting it. Especially in the morning. I think it has something to do with oil pressure. Because when i crank it over in the morning it takes a good 6-10 seconds for it to start. And I have noticed that there is not pressure for the first 5 seconds I crank it. And it fires up when the pressure hits about 30 psi. After it starts i have good pressure about 90 at first the drops to about 60 when its warm and it runs normal. I can turn it off and restarts normal. I can even drive it to work and have it sit for about 8 hours and it fires right up normal. But if I let it sit for more than 12 hours it takes 6 - 10 seconds to fire up. One thing that I did notice is she has a non-4X4 radiator in it and whoever instaled it bypassed the oil cooler in the radiator bacause of a wrong size fitting. I am planning on installing a stand alone oil cooler soon. just haven't had the time yet. I was thinking that maybe the oil was draining back in the pan from the cooler lines being looped and tied off in a high place. Any help would be great.