But trust me, if it smells funny and you happened to get it from your Grandmother's house (who rarely used the dishwasher) and it could be 3-10 years old, just don't use it. Really. It's not worth it.
I started my dishwasher with the old liquid dishwashing detergent (not regular dish soap, I learned that lesson in college) and then started icing a cake. After icing the cake I went to put the knife in the sink and saw lots of bubbles. Then I turned around and saw this:
After a few shreaks and dancing around I turned off the dishwasher and then grabbed my camera (of course). Then did some google searching and found out that yes, dish washing detergent can go bad. Something about the liquid separating from the detergent agents or some kind of chemical reaction.
After googling some remedies I went back to figure out what to do. I realized the machine was still on the pre-wash cycle and hadn't even opened up the full detergent box. So I scooped all that out and tried starting it again.
Unfortunately there was still enough of the soap in the pre-wash part that bubbles still came pouring out of the bottom. I had to catch them with a couple of 9x13 pans that I had to keep emptying out and switching out.
So I stopped it again and took out the bottom rack and scooped as many bubbles as I could out and tried running the rest of the cycle out like that. Finally I got it all cleaned out.
Positives were that it happened during nap time (don't need to make the kitchen floor a kiddie water park thank you) and the floor did need to be mopped anyway. I tell ya, if it's not my kids making the mess it's me!