Did you cover the electronics on it? If not, more than likely there's some cleaner/water messing with something. I'm not familiar with the 3.7's, does it have a distributor? If so, you might have some water inside the cap. Pop it off, check it, dry it out if need be and try again.
If you ever clean your motor again, just use straight water while it's running, or while cool go over it with some simple green and spray it off and let it dry out. Always cover the electrical stuff.