Ok, so I used a coffee can to make a chocolate cake, I lined it with wax paper, added chocolate pudding, and preheated the oven at 310 and it completely sunk in the middle. It know looks like a bundt cake. I used DH cake mix. What did I do wrong?

You didn't say what pan size, I use DH's all the time, bake at 325-350 depending on the size. I only get the dreaded sunken middle when I open the oven too soon, if it's even a little too under done it'll sink, I leave it in for at least 75 min before I even touch the oven door. Hope this helps a bit, good luck!

I used a coffee can, and I usually wait 30-40 minutes before I open the oven door to check on it.

Sorry I reread your post and saw that you said you used a coffee can I would definitely wait longer, especially at 310, it is going to take a while to cook through. Have you tried baking strips? Sometimes I use them and sometimes I don't, they usually seem to work pretty good. I would buy a couple DH mixes(last I checked they were really cheap at Walmart) and try leaving it in the oven for a good hour, hour and 15-20 min and see how it goes. Good luck!

310 sounds like too low of a temperature. I would try setting oven to 330. I was having trouble with my choc. cake sinking in the middle and found that if I lowered my oven rack 1 notch it really helped.

I had that happen when I over filled the pan and neglected to put a nail in center. It was like poof and sunk grrrrrrrrrrrrr hate when that happens