95 7.3l Fuel Pressure issue... or is ther something else?
 

First... many thanks in advance to anyone collaborating with this thread. I hope I'll be able to return the favor some day.

Then... my dad lived in Argentina, I lived in Vietnam. He passed away, I returned to Argentina to take care of his business and... his truck:

1995 F-250 7.3l Auto 4x4 Heavy Duty with (I believe)
The truck is in good shape, rarely used for work, mostly grocery getter.

I started using it and ran ok for the first month. Then it started doing very short (1/4 second) misses, usually at highway speed. Then the misses became complete engine shutdowns for 1 or 2 seconds. Then the engine would start again. It would be very random. Finally, it would stop running 100%. I would wait a few seconds, or a minute, and start again. (Nice description of a CPS failure... right?)

Parts are very difficult to find here.. so I ordered a CPS sensor, but kept using the truck, taking the risk. But the next few failures where a little different, the engine would still run but loose power, misfire, then run ok again for a a few more miles. It did that about 3 times, until the power did not come back, but it ran enough to get me home.

I shat down the engine and it never started again. Eventually the CPS arrived and I was hoping that was going to be the end of my troubles. Changed it. No start.

I started to suspect fuel starvation. I brought down the aft tank, opened the sender, inspected lines, blew air through both pick up and return lines, checked tank selector valve, blew air on all lines again... all clear. I emptied the fuel filter bowl, checked all lines, blew air. Clear. Installed all again.

So next, with the filter bowl empty, I checked pressure at the shrader valve, and at the same time checked if bowl is loaded with diesel. Pressure barely reached 3 psi and fuel was coming up very slowly. I imagined I had a bad fuel pump (original mechanical pump on this one). I was very lucky and found a new pump in my dad's garage. Changed the pump. Cranked and pressure started to come up very slowly. Opened the filter bowl, filled it up with diesel, closed and cranked again. Pressure started to climb and continued to climb very slowly up to 35-40 psi. By the time I got there I was running out of battery. Engine did not even once showed signs of firing. After cranking fuel pressure will not come down. After 45 minutes the pressure was still at about 30 or 25 psi. Is this normal? Does the fuel system remain pressurized?

Of course I suspected Fuel Pressure Regulator bad. Opened every hole on it but could not find anything wrong, other than a plugged screen, that was cleaned in minutes. The rest of the FPR looks ok, but don't have data about ho to check if it is actually working ok.

This is all I have...don't know what to do next. Suggestions?