V10 fuel pressure

What should the fuel pressure be on my 01 V10? The repair manual says between 35psi and 45psi. But I just read on a V10 site that 54psi is what it should be. does any one know what I should be getting?
I am having a big power loss with the engine under load and suspect the fuel pump. I checked the pressure with a cheep pressure gauge and it read 60psi but when I detached it I found it wasn’t zeroed and read 12psi with nothing attached so if it was still working correctly then that would put me at 48psi.
Also does any one know if the pump has to work harder when driving or is it the same at idle. If the pressure checks out at idle then it should be the same under load. Is their a way I can check the pressure while driving?

I would go with the service manual figure first, so it sound like your pressure is ok, did you check it under a load or at idle ????

I replaced one of the o2 sensors because it was throwing a code and it fixed the problem. I guess it was getting a high reading and leaning the fuel out. That’s caused the whole power loss. I can’t believe that that one bad sensor had that much affect on the performance of the truck. If anyone else has a similar problem I would suggest replacing the o2 sensors. They cost about $40 each and what a difference.

to test your fuel pump do a " dead head " test, do this by hooking up a fuel pressure gauge and clamping off the return line briefly to max out ur fuel pump pressure. im not sure that the spec is for ur pump.

There is no return line on a V10 fuel system.

oh ok i wasnt sure about that. If it is a returnless system it will have a regulator built in the sending unit in the tank and the regulator will change with engine speed, im not sure on the specs but check pressure at idle and then at a certain rpm according to the specs.

It should be around 49 or 50 at idle. After you shut the truck off it should not drop below 35 after 5 minutes. You can isolate the regulator by pinching the supply line with a clamp.