Any details about the truck, its history, & the history of the symptom would make it a LOT easier for anyone to offer useful suggestions. You should put ALL your truck's details & history (as much as you know) into your signature(<-click that) so it shows with each post, as this page explains:

(click this text)


Phone apps don't always show signatures, so you may need to switch to a real browser in desktop mode on your phone, or just use a desktop/laptop computer. Put your location (nearest city) in your profile &/or signature, & upload an avatar of the truck. Not all its details are relevant to these issues, but you don't necessarily know which ones are relevant, so just put everything in now. The more pics you post (NOT in your sig) of the truck, engine, wiring, labels, & undercarriage, the more likely we can help you.

 

Welcome,
Post your issue in this forum. This one is for introductions.
You can use a jumper cable clamped across the big lugs on the glow plug relay to activate them.