I was given an iPhone 4 by a friend who lost it in the snow. He found the phone after apparently a car drove over it,...

While putting the iPhone 4 back together after replacing the front screen assembly, I lost the nut from the logic board...

Try jailbreaking it with some other software, or with the firmware that you currently have on the iPhone, not the latest. It might not be because the water damage, a couple of weeks ago I jailbroke my iPhone using latest firmware, initially having an older firmware, and it didn't have any signal, no wifi, no bluetooth. What I did is update the firmware and then jailbreak, it worked.