As a visitor entering the US I have no rights, and my story is not all that uncommon.
Border Services are not required to fix a car they have taken apart.

The last time i drove to the US was about 4 years ago my brother was trying to get me to buy property by his place (before he sold)
After almost 3 hours at the border the guard sad to me in front of my wife and kids
I would like to keep you longer but I dont have a legal reason to.

Bare in mind I am always polite and honest with them