High Fuel Rail Pressure

[Eman]

This is both with the stock and performance tunes.

Are you retuning it? I would erase everything and get a stock program put in. Sounds like your programming is your problem.

 

[FarrukhAnwar]

I tried erasing everything and going back to stock but it still did the same thing.

 

[RGLL]

My 2006 V6 with 162,000 miles (all stock), does the same thing and the PID values for fuel pressure will be about 10 psi higher than what you see on a physical gauge. The service manual states how the PID values are higher than a gauge. I have a fuel gauge plumbed into the fuel rail and when the engine is cold it reads around 30psi and my scanner will show 40 psi and when fully warmed up it will be about 50 psi on the gauge and 60 on the scanner. The pressure also fluctuates all the time around 3 to 5 psi and I think that's just the PCM continually adjusting the speed of the fuel pump.

 

[RGLL]

While diagnosing a hot start problem I had reason to test the fuel pressure at WOT several times and saw that regardless of what my scanner was showing while driving (about 60 psi) that when I floored it the pressure would drop to about 45 gauge psi and the limit according to the manual is 37 psi gauge. This was before I changed just the fuel pump motor to cure the hot start problem. You have codes for defective O2 sensors and that might be the problem. Hook up a vacuum gauge and check for intake leaks and also do a smoke test if you find that your vacuum is not good. Hope you get it running good.

 

[FarrukhAnwar]

Thanks for the response! I verified that everything in the fuel system is mechanically working properly by hooking up a physical fuel pressure gauge, using a multimeter on various components, and monitoring/cross-referencing the live data. The O2 sensor codes appear to be from an actual rich condition rather than from defective sensors. On a cold start, the engine temperature is cold, and the fuel rail temperature is cold, so the PCM asks for the regular fuel rail pressure of 40 PSI. No codes are thrown and the fuel trims are close to 0. However, as the engine heats up and the fuel rail temperature subsequently heats up, the PCM starts asking for more and more fuel rail pressure until the desired fuel rail pressure (and thus the actual fuel rail pressure because everything is mechanically working fine and is just listening to the PCM) reaches over 75 PSI, in which case, the High Fuel Rail Pressure code is thrown, and because of the high fuel rail pressure, the long term fuel trims become very negative at -15%, in which case the O2 Rich sensor codes are thrown.

 

[RGLL]

Do you have a tune? Perhaps that is why your fuel rail pressure is reading 75 PSIG when fully warmed up. Mine reads 55 PSIG when fully warmed up.

 

[RGLL]

Did you put an aftermarket FRPS on it ?

 

[FarrukhAnwar]

I went back to the stock tune, and it was still having the same problem. The FRPS is the OEM one. You bring up an interesting point though. I looked back at the data again, and most of the time the fuel rail pressure consistently increases but I haven't seen it go above 65 PSI yet (or maybe I haven't driven it long enough in hot enough conditions yet for it to reach 75 PSI on its own). However, there are random points where the FRPS reading temporarily spikes to 75.99 PSI, and I am assuming that it is only when this happens that the High Fuel Rail Pressure code is thrown. So maybe the OEM FRPS is on the way out. But for the most part the FRPS works fine so I'm still trying to fix the underlying behavior of the car asking for such a high fuel rail pressure, as it is causing it to run rich and hurts its fuel economy.

 

[AJT24]

I went back to the stock tune, and it was still having the same problem. The FRPS is the OEM one. You bring up an interesting point though. I looked back at the data again, and most of the time the fuel rail pressure consistently increases but I haven't seen it go above 65 PSI yet (or maybe I haven't driven it long enough in hot enough conditions yet for it to reach 75 PSI on its own). However, there are random points where the FRPS reading temporarily spikes to 75.99 PSI, and I am assuming that it is only when this happens that the High Fuel Rail Pressure code is thrown. So maybe the OEM FRPS is on the way out. But for the most part the FRPS works fine so I'm still trying to fix the underlying behavior of the car asking for such a high fuel rail pressure, as it is causing it to run rich and hurts its fuel economy.

Hi, I have a 2001 Mustang 3.8 and its doing the same thing. Initially I had FRPS code and Bank 1 system code. I replaced the FRPS drove for 110 miles and then the codes cleared. Waited a day in between. I plugged in the reader in today to make sure no codes exist and bam, Frps code pops up again. But this time the code reader says High Output.
My thinking is it has to be the aftermarket part that I put on.
I did the same for my Charger by installing an aftermarket thermostat- it works but the temperature now gives erratic readings and as before with the OEM reading was normal.
So I say it's the aftermarket part that's making it have a higher output Probably the same for your situation.