You have a tough problem, and such poor advice as in the first answer won't help. Undoing 6 years of mistreatment won't be easy. The first step is to go to
https://www.askmehelpdesk.com/dogs/i...tml#post251802 and read through the sections on What does a puppy need and Housebreaking. They are heavily oriented towards young puppies, but much of the same applies to older dogs.
Not even watch dogs keep schedules. Likely he is used to going when he has to go wherever he is. It is very tough retraining dogs that have been forced to live in their own filth. Using the signs I suggested, try to anticipate when he needs to go out. It is possible he was trained to have bowel movements on pavement in an urban environment or even lived somewhere without access to grass. Find a grassy place to walk him frequented by other dogs. Keep walking, but give him plenty of chances to sniff around. Even a neutered male will be tempted to leave his mark in the grass like the other dogs. When he does, praise him as I discuss in the sticky.
As I mention in the sticky, he must see you as the leader. It is the leader's job to take care of the pack. Here are some additional ways to show him you are a caring leader. ''Elevation for small puppies: Sit on the floor and gently put your hands around your pup's middle, below his front legs, and lift him up. He is facing you. Hold him for 15 seconds. Repeat until he no longer struggles. If he is past 10-12 weeks, lift his front feet off the ground, but don't pick him up.
Cradling for small puppies: Hold your puppy gently on his back, as you would cradle a small baby. If he struggles, hold him firmly until he quiets for 10-15 seconds. With larger pups, you can do this as your sit on the floor, with your pup between your legs.
Quiet lying down: Place your pup on the floor on his side, with all 4 legs pointing away from you. Use your hands on his neck/shoulder area and middle, to hold him in this position. When he is quiet, praise him. Lengthen the time that you keep him quietly in this position. When he accepts this position well, handle his paws and muzzle, while keeping him quiet.''
The quotes mean this isn't my original work. It is copied from my Puppy Raising Manual. I have long used these or minor variations of them, and they are very effective. You may want to give him a belly rub while he is on his back too. Helps bonding. There is a big difference between him rolling over and demanding a belly rub, and you choosing a time to roll him over and rub his belly. The latter cements your place as pack leader.
It would help if I knew if he had been crated before. Just why some dogs fouled their crate almost immediately like that is hard to say. I don't trust people that insist they know why a dog does anything. I have never had a dog do it. I think it may be stress more than anything. None of the books I have ever read even acknowledge such a problem exists, let alone give a solution. I think it is the stress of being left alone. He may have been shut up by himself all day, and fear every time you leave, it will be hours. Being by himself all day is not natural for a dog. If you take the suggestion to abandon the crate, it may be the rug or sofa instead. As long as he is just urinating, the grid that I suggest in the sticky, reduces the consequences, giving time for other measures to work. Tiring him out and laying down in front of it may help. If he is highly food motivated, a Kong filled with peanut butter could work wonders.
I am slow to suggest medicating a dog, but this may be a case for it. If you haven't already had him to the vet, schedule a visit as soon as possible. Who knows how far behind he may be on his shots. If you have mosquitoes, be sure and have a heart worm check and get him on a preventative. The flea season is winding down in much of the country now. If he doesn't have fleas now, you may not need to worry. If you can see or feel dark, reddish specks at the base of the tail, he does have fleas even if not enough to see. Ask the vet about effective treatments. Likely they are already in your yard and house too and will require treatment. With the modern preventatives, it is easy to keep fleas away, but tough to clean up an infestation.
I want to thank you for giving this dog a home. You mayhave saved his life. Older dog are hard to place, and with good care, he could be a joy for many years once you work through the problems.