Whew! This is a tuffy. Keep at it. I can't add anything but it seems like a right track kind of thinking to me. Post #8 & 9 are very good.
I think I would try a new pump.
I've by-passed the electric pump and still have the problem but I have not by-passed the mechanical pump(I can't believe the brand new Carter pump is already bad)... I have forgot to do that for some reason. Thanks rumble for reminding me... LOL
