[Donor]

I'm assuming he has checked to make sure that it indeed is the fillport and not something else Near the fillport?

If it's indeed the fillport, make sure it's tightened very well (though I'm sure he's not that "gifted", to leave it lose. heh) Try the teflon around the thread incase the Oring is shot.

But in my opinion, if it's escaping that quickly, I'm thinking the input valve might be stuck on open... maybe a grain of sand preventing it from closing?

Does it do it only on a light load? Get him to try to fill the mag to the top with gas. (I'm wondering if the pressure of a full load will be enough to crush whatever's holding the valve open... effectively closing it...[if the valve is indeed the problem])

Goodluck!