Problem is on a 2005 Ford E-350 XLT Super Duty 5.4 2v, 230K miles
Check engine light came on. Scanned it and found the code P0191, which is for the Fuel rail pressure sensor performance. Truck MPG went down severely but drove fine. Looked around everywhere and everyone said to replace the sensor. Went to NAPA and got my new sensor, installed it, reset the codes, ran fine but now has a code for p0193.
New code is for "Fuel Rail Pressure Sensor Circuit High Input", along with two O2 sensor codes for banks 1+2 sensor 1 running rich. Checked the fuel pressure on the scan tool at idle after replacing and it said 39-41 PSi. Then I checked the FRP after the new code came on and it reads 75+ PSI which is clearly way too high. What could be causing this? Truck runs fine but is now getting 2-3 mpg. Need my van for work as soon as possible.
Thanks
Possibly your fuel pump is putting out too much pressure or your fuel return line is plugged up, letting excess pressure build up. (Rockauto doesn't list a separate fuel pressure regulator for that vehicle. It might be built into the pump.)
Now that you say that, since these issues have started I occasionally notice a bad sound from the tank area when the key is in the run position. It's a high pitched just bad electric sound. It would make sense if the issue related to the pump acting up, I was thinking something with the wiring. I've got a 7/8ths full 32 gallon tank right now... ugh. Would you agree that I need to compare the fuel pressure reading I'm getting from the scan tool with an analog gauge? Unfortunately on these vans there is absolutely no working room...
If feasible, yes, checking with a mechanical gauge would be good. I suspect the pressure really is too high though, given the poor gas mileage and overly-rich mixture.
In case anyone finds this topic later with the same issue, turned out that the fuel pump was running at full power at all times due to an electrical short in a module that controls the pump located on the frame near the spare tire in the rear. Analog gauge read upwards of 106 psi 😬 A rust hole in the protective cover that is bolted to the frame allowed water in from an undercarriage rinse at a carwash. Had a shop put in the new module for approx 130$ with labor included, and luckily the o2 sensors weren't fouled from the mixture being too rich.
thanks for following up