I've chased this problem for a couple months now and no progress. It's a 2001 King Ranch automatic with the 5.4. 4x4. It ran perfect up until one day all of a sudden when I shift it into gear it stalls, no codes on my innova scanner. I've been through the vacuum lines, transmission sensors, EVAP system and no change. I have been able to get it into drive and drive it but it's lacking power unless you put your foot in it. I know my fuel pressure is 28 psi at idle but no change when I unhook vacuum to the regulator. Also the check valve is not holding pressure on the rail after turning the key off. Before I change the fuel pump is there anything that I'm missing???

 

Reg is not working for one.

Anything below 32psi is when these pumps can periodically freeze up.

Chk FF as well.

 

I changed the fuel filter and did try another regulator that I had on a spare manifold, but it could be bad as well. I'll try a new one next before I change the pump. I was curious about the pressure because to me it sounded low and given the fact I'm second owner of this truck and the body has 250,000 miles on it the pump is probably shot.....