This may seem kind of stupid, but please trust me, and try it.
Get some GOOD jumper cables, and connect them to another truck, and to this one.
Let the other truck idle for maybe 5 minutes. High idle is best.
Now, let your glow plugs cycle normally, and then try starting.
If it works, check your alternator and batteries. Mine seemed perfectly fine. Truck just WOULD NOT start. Crank and crank and crank. Cycle the brand new glow plugs, until even I was red in the face. Charge both batteries to full charge with a charger. Did this several times over about a week... No start. Jump it after letting it charge up from the other truck for 5 to 10 minutes... Started right up.
Try it. If it does work, first thing I'd look at is the alternator. It may be 'working'... Just not working well.
89 F250 XLT Lariat 7.3idi C6 4WD
92 F250 XLT Lariat 7.3idi E4OD 4WD
Last edited by Selador; 05-16-2019 at 07:10 PM.
Reason: additional info