f250 7.3
So the fuel filter (or so I believed ) was getting worse and worse and finally the truck didn't turn over.
Went and got a new filter (screw on - looks just like an oil filter - with a drain nut on the bottom) and once I got the air out of the system she roared to life.
No problems for three days - then a short period when 'water in fuel' & 'fuel filter' came on - cranked a couple seconds long - turned over no further problems that day.
It has, over the the last week and half, gotten worse and worse until today - once more, it simply won't turn over. Exactly the same as before I got new filter on.
Checked going from front to rear tank - no difference

No white (or any colour) belching from exhaust. Schirvner(?) value shows decent fuel pressure/quantity. 3/4 tank of fuel (1/2) tank put in Tuesday (this being Thursday) Injection pump new last new --- and YES - all the fuel lines ARE the old grey originals.

The thing that is really confuses me is the working great then quickly but incrementally getting worse.

Hoping you all can give me some good idea's over the next 24hr or so because the vehicle is at my-in-laws and will be going back over o further trouble shoot Sat afternoon.