dodge ram diesel break trouble

1996 dodge ram diesel 2500 cant break the rear weel when the truck is on a jack dont seem to have much pressure on the rear weel and there is no air in the line the front is good and the abs ligth is not always on it turn off once in a while and the break dont change . it was never low on break fluide the only thing that append isthat i had to change the spring kit can someone help me

I assume you have rear drum breaks and replaced the springs. Their is an adjuster for the shoes. They have a brake adjuster tool with a rubber plug you remove for axcess gradually tighten it until the shoes barely rub the drum.
If this is good pull the drum on the otherside and make sure all parts are installed the same.
If you drained the system you might to pressure bleed or go to a shop with a scanner to properly bleed. Try shoe adjustment first.