Fuel Rail Pressure Sensor

[fwtex]

Symptoms for possible diagnosis

I have a 2004 Sport trac with 200,000. Last year it started cutting out on the evening drive after about 30 minutes in hwy traffic. Acted like it was cutting out but restarting itself right away.

This went on for a few days then everything ran fine for a few months. Check engine light comes on and code is P0193 for fuel rail sensor. This continues on like this where it would act up for a few days then be fine for a few weeks. All winter it ran fine but as soon as the temps started rising it would again start to act up every now and then on the evening commute drive.

This week the problem escalated to its worse yet of missing badly on acceleration, stalling but starting right up and then cutting out when trying to drive. Lots of missing(backfiring ?) and no power at all.

I let it sit for about 30 minutes and it has now driven for 3 days with no sign of any problem except the light is on.

My thought is that the problem has something to do with the temperature since it does not act up in the morning and did not act up through the winter.

Should I replace the fuel rail sensor or is it maybe a connection or wire overheating?

 

[imp]

I have a 2004 Sport trac with 200,000. Last year it started cutting out on the evening drive after about 30 minutes in hwy traffic. Acted like it was cutting out but restarting itself right away.

This went on for a few days then everything ran fine for a few months. Check engine light comes on and code is P0193 for fuel rail sensor. This continues on like this where it would act up for a few days then be fine for a few weeks. All winter it ran fine but as soon as the temps started rising it would again start to act up every now and then on the evening commute drive.

This week the problem escalated to its worse yet of missing badly on acceleration, stalling but starting right up and then cutting out when trying to drive. Lots of missing(backfiring ?) and no power at all.

I let it sit for about 30 minutes and it has now driven for 3 days with no sign of any problem except the light is on.

My thought is that the problem has something to do with the temperature since it does not act up in the morning and did not act up through the winter.

Should I replace the fuel rail sensor or is it maybe a connection or wire overheating?

I would say that what is happening, is that the Fuel Pressure and Temperature Sensor has been acting up quite awhile, and has likely now quit. Under those circumstances, the computer does not know what to do to keep fuel pressure at normal level, and it may go into the "Limp-Home" mode mentioned, where the engine continues to run, but only poorly, indicating trouble ahead.

I would replace the sensor. Mine cost about forty bucks, as I recall. imp

 

[jon_s_brady]

I found a photo of a fuel pressure sensor on Rock Auto from a different angle.
View attachment 74692
It looks like it may bolt up to my stock fuel rail.
View attachment 74693
Or even to my new Banshee fuel rail.
View attachment 74694

I assume the top port is a vacuum connection and there is a diaphragm to provide dampening.

Thanks for offering to provide me wiring diagrams. Since the sensor outputs go to the PCM (which I won't be doing) the only thing I need to know is which pins/wire colors are for pressure and the supply voltage provided by the PCM. I'll PM you my email address so you can send me the engine control page showing the sensor as an attachment.

I'll try to purchase a used sensor with mating connector and pigtails. My stock fuel pressure was 62 psi but with the Stealth pump it has increased to 67 psi which will richen my AFR when the PCM is in open loop. After installing the fuel pressure sensor I'll bleed the pressure down to 62 psi and measure the sensor output voltage.

I'd also like the wiring diagram showing the connections to the FPDM. The photo shows more pins on the connector than I expected. I expected two pins for power in from the inertia fuel shutoff, two pins for power out to the fuel pump and two pins for the motor speed control from the PCM. Maybe to save wire routing Ford ran the fuel tank pressure sensor wires and the fuel level sender wires thru the FPDM. If I used the Ford FPDM would only use the power input, output and control lines. I would have to determine the control voltage that results in 62 psi and then match that with the 62 psi sensor output voltage. The Ford FPDM may not have the capacity (215 watts) to control my Stealth pump at max flow rate. However, I have no need for the max flow since it supports 700 bhp.

I am also retired but only 67 years old. I enjoy working on automotive projects especially those involving electronics.

I'm a little confused...no, let me be honest...totally confused. I inserted, inline with a T fitting, a fuel pressure gauge on my 2005 Explorer XLT 4.0 SOHC right where the fuel line meets the fuel rail. It measured 30 psi after I had primed it with three on/offs of the key. I then started the engine and at idle it shows a pressure of 30 psi.

Believing that the fuel pressures of models after about 2002 increased their pressures to 60-75 psi I reasoned my P0171/rough idle/skyrocketing LTFT1 may be due to a low fuel pressure. I therefore replaced my fuel pump.

After installing the new pump I get the very same fuel pressure - ~30psi.

I keep reading two pressures - one of ~30-40psi and the other of 60-75psi.

For a 2005 Ford Explorer XLT 4.0L SOHC EFI can someone tell me defintively which is the correct pressure range? If it's the 60-75 psi range, I'm also open to suggestions why it's reading low. And I have already put in a new fuel filter to remove that possible reason.

 

[2000StreetRod]

30 to 40 psi is normal

If you check post 19 of this thread you'll find that normal fuel pressure for your vehicle is 30 to 40 psi. Thru 1998 Ford installed a lower pressure return type fuel system. For 1999 thru 2003 Ford switched to a higher pressure (about 65 psi) non-return fuel system. In 2004 Ford installed a fuel pressure sensor on the fuel rail and the PCM controls fuel pressure via pulse width modulation. See: What's that on the fuel rail?

 

[jon_s_brady]

Sir! You are both a scholar and a gentleman! That was perfectly put. Sorry about missing post #19 . I did actually read that but didn't realize the links under the line were meant to be followed. I had taken your text as the totality of your comment...I should have known better.

So that answers my fuel pressure questions. With 30 psi in the fuel rail that doesn't sound like my issue then.

You wouldn't happen to know the expected intake manifold vacuum for the 2005 4.0 SOHC would you?

My OBD scanner is telling me 17.7 in Hg at idle (750 rpm). I put a gauge on and connected it and it read 18 in Hg. While at the low end of the range it seems like it's within an acceptable range. I smoke tested the engine and couldn't find any smoke escaping so I'm thinking vacuum isn't my issue either.

 

[2000StreetRod]

vacuum reading

I don't know about the 2005 but for the 2002 SOHC V6 the intake manifold vacuum with a warm engine at idle is specified as 15 to 22 in-Hg depending on engine condition. As I recall my 2000 with 150K miles was about 20 in-Hg stock and changed to about 15 in-Hg after I added my supercharger. Your 18 in-Hg seems reasonable.

Since you apparently don't have a fuel pressure problem you may want to switch back to your other thread since it describes your symptoms and what you've tried to fix the problem: Long Term Fuel Trims Significantly Different Between Banks

 

[Coleon]

SOHC engine, right? Yes, it has a fuel pressure relief valve. I can't link directly to the Ford manuals, but this is good enough: http://www.autozone.com/autozone/re...epairGuideContent.jsp?pageId=0996b43f802e3ddb

I looked through all the system info and troubleshooting and diagnostics sections but couldn't find an exact number on what the valve opens at. But the PCM is programmed to go into limp mode after any kind of serious sensor failure, so I assume that fuel system would be a very high priority for it.

I would love to know what resistance that high pressure fuel pyump sending unit sensor is putting out to the ECU. I'd love to throw a XXXX oihm resister in there and see if I can work around the Limp BS..

Am I off Here?....

Thanks