Are you interested in selling the truck? Let me know.
Inspect the glow plug wiring real close for the burning smell? I assume you are pressing on a button to "energize" the glow plugs? Do you have a volt meter? If you do check the resistance thru each glow plug. The one that is "different" will probably be bad. If you are glowing manually press it and count to 10. That should be plenty.

Let me know if you want to sell it "as is".

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Jim