If your truck battery is getting weak, then buy a new one.
If you’re engine is getting old, worn, low compression, dud glow-plugs etc. then you seriously need a good big traditional battery to keep cranking it until it starts.
A jump starter is not a substitute for a decent battery. If it sits for months, then a little solar panel under the windscreen will keep it tip-top.
These sort of jump starters generally use bagged LiPos, not LiIon, stressed to the max. (and beyond, no limits usually). I would not want to keep one in my vehicle, or anywhere inside my property.
They do work, but they scare me.
I would trust something using super-capacitors to turn the engine over a few turns, and have even considered making one myself, with a motorbike battery to energise it.
Sorry if I have mis-understood.