doberkim pointed out an important detail: diarrhea isn't an illness by itself, it is a sighn that there is an underlying problem the body tries to deal with.
the best thing to do (if there's no underlying problem that your vet has confirmed) is to fast the dog a few days to give the digestive tract a chance to heal and recover, and then start back up with a bland diet, such as for example boiled chicken and rice.
as long as the body has to use its resources for digesting food, it can't fully focus on healing, that's why fasting is so important. many animals already know this and refuse food to begin with, but often owners are concerned and want to get their pet to eat at all cost, which is not a good idea, especially if the dog also runs a fever.
if stools are a little loose, pumpkin (and some other natural remedies) are a great way to get things under control, but full-blown diarrhea, especially if it is going on for any unreasonably long amount of time, is nothing to fool around with.
if the dog is otherwise ok, my preferred course of action would be a 2-3 day fast (young puppies no longer than 24 hours tho), with honey water or thin vegetable broth without solids as the only "food" given during this time. giving pedialyte is a good idea, to restore electrolyte balance.
after the fast i'd start slowly with a bit of slippery elm bark mush and small amounts of bland food.