Until recently I could jump in and start her up....now I must wait until the "Wait before Starting" light goes out....about 30 seconds. Batteries are
fine. Is this a problem with the heating Core, as there are not any glow plugs?

 

I don't see how it's a heater grid problem since you say you were able to start it just fine before without having to wait for the heaters to warm up. What does it do if you try starting it like before? No glow plugs on these trucks.

 

There is nothing.....dead, until the lights go out and a few seconds after that.

 

If you turn the key before the lights go off it doesn't even turn over? Sounds almost like the grid heaters are pulling too much power, but I don't see why that would be. Where are you located? My grid heaters don't even come on right now. I think they don't until below 40* F anyway.

Other than that, battery connections/grounds would be my suggestion, but I don't know why it would start after the lights go out. Strange indeed.

 

Check the trigger wire going to the starter. I had similar problems with it not starting at times, sometimes id just let it sit and try again later and it would start. Connection going to starter was deteriorated badly. New crimp on eyelet fixed it.

 

unhook the grid heater power from batter to the relay on driver side then try it