Glow plug system
 

I am working on a 92 2500 with the 6.5 turbo. I have replaced the glow plug relay on it and it still won't start without jumping the poles. It's not the fusible links from the relay to the plugs or it wouldn't even start then. The glow plug light isn't coming on in the instrument panel either. Is there another fuse or relay that I'm not seeing. TIA

I also have a 92. Every so often I get the same issue with the glow plug light not coming on. It will turn over but not start.
So far a simple cleaning/tightening of the battery cables and grounds has fixed it.

I've done this and still nothing