2004 Liberty 3.7L high fuel rail pressure

[04Liberty#!]

2004 Jeep Liberty 3.7L w/ 183675 miles
Codes P0132 and P0152 (high Voltages at upstream O2 sensors both sides) Lean
Fuel Rail Pressure is 60 to 65psi at 750rpm idle. Online info states fuel rail pressure should be 49 +or- 5psi
Dealer tells me needed parts are obsolete and I need to replace complete fuel tank with upper and lower fuel pump assemblies.
I have already recently replaced; cats, O2 sensors, coils, injectors, lower Fuel Pump Assembly (twice)
I believe the Fuel Pressure regulator is the issue. It is housed in the upper assembly.
After market suppliers have pressure regulator on smaller tube on lower assembly.
I have tried two but believe the regulators are not to 49 psi spec.
No sign of vacuum leaks. I did not remove regulator in stock upper fuel assembly when trying the new lower assemblies.
I am considering putting a pressure reducer inline before the fuel rail.
Thoughts?

 

[DadOSix]

X

 

[04Liberty#!]

Update:
Fuel Rail pressure at 750rpm idle is 65psi w/ needle bouncing +or- 3psi.
Engine running seems to be running smooth.
I pinched the flexible fuel line just upstream of the fuel rail as much as I dared.
RPM dropped to 650, pressure dropped to 62psi +or- 1psi, engine running smooth.
Thoughts?

 

[04Liberty#!]

Update:
I took out and reinstalled the old Fuel Pressure Regulator (FPR) in the upper assembly without the smaller O-ring.
To allow flow to the new FPR just below the upper assembly, leaving the large O-ring to prevent an always open return.
Primed the system a few times with the key and it started right up.
At first, idle smooth at 1200 to 1000 rpm with a Rail Pressure of 55. (Spec for the Spartan)
Confirming (to me) the old FPR in the upper chamber failed closed preventing flow to the new FPR just below the upper assembly.

At first when I revved the engine, it ran rough and miss fired. Sounded to me like air in the line.
A minute or two later, The idle rpm dropped back down to 650, keeping 55psi on the rail and running smooth.
But when I drove it, it stalled. After the first stall pumping the gas pedal keep it running enough to get back to the shop.
It felt to me like fuel pressure to the fuel rail was intermittent and/or with air. This triggered a number of new codes but not P0132 or P0152.

I; turned it off, cleared the codes, set up the fuel rail gauge so I could see it, started it up again.
It idled smooth, at 650rpm and rail pressure at 55 +or-1, when I revved it in between 650 and 3000 rpm.

Perhaps: the ECM is resetting things to the lower rail pressure.
And / or the old stock upper assembly without the lower o-ring on the FPR is allowing air in the fuel line.
Dealer and on-line sources tell me a new or old upper assembly is not available.

FYI: I had to change the wire connectors on the new lower assembly to connect to the original upper assembly.

Thoughts?

 

[DadOSix]

I am so confused by your process.

Are we looking at 2 separate issues?

 

[04Liberty#!]

As always there are probably many issues.
Your first response on my end was blank.
I am asking for information that may be helpful.

I believe:
The OEM FPR failed closed causing high rail pressure which eventually burnt-out CAT and Coil. The OEM FPR is no longer available.
The repair parts recommended by online sources (LFPA) are out of spec. High Pressure and wire connectors don't mate with OEM UFPA.
A new mating UFPA (now called a tank flange) is also not available.
Dealer tells me the whole fuel system including tank need to be replaced.

I'll send some pictures later today that may help clarify.

Thank you

 

[DadOSix]

As always there are probably many issues.
Your first response on my end was blank.
I am asking for information that may be helpful.

I believe:
The OEM FPR failed closed causing high rail pressure which eventually burnt-out CAT and Coil. The OEM FPR is no longer available.
The repair parts recommended by online sources (LFPA) are out of spec. High Pressure and wire connectors don't mate with OEM UFPA.
A new mating UFPA (now called a tank flange) is also not available.
Dealer tells me the whole fuel system including tank need to be replaced.

I'll send some pictures later today that may help clarify.

Thank you

True - I had a thought but my internet timed out.

I can't see why the fuel pressure would be responsible for cat and coil issues. A rich condition, maybe, but enough to burn those out? I dunno.

Initially, it seemed like you were chasing the downstream o2 sensors with respect to fuel pressure. IMO, and it is just that, my opinion, the 132 and 152 codes are pointing at electrical issues on the control side, not the feedback to the ecm. From what I read, the High voltage flag is setting because the sensor is seeing greated voltage across the sensor. There are 2 circuits - one that powers the sensor (and heater in the sensor) and the feedback loop to the ecm. So the 132 or 152 look like the sensor power is shorted to 12v somewhere. Note - it could be ANYWHERE as these jeeps are 20+ years old and did not use the best wiring. So, I would start at the sensor and chase backward - not just visually, but actually pulling, moving, jiggling anything in the wire path.

I know you state now that the codes are gone, so i dunno where things changed.

A few pics would definitely not hurt.

 

[Intermechanico]

Fuel trim (time injector is open) is directly related to fuel supply pressure. If the pressure is higher than normal, more fuel will be injected over a given period of time.

The ECM adjusts fuel trim to accomodate component wear, but only to a point, and it is not instantaneous.

If your fuel supply pressure is siting at 60-65 psi, or 10-15 psi above the 49 psi specified pressure, the system will overfuel up to 20-30%.

The ECM will adjust short and long term fuel trim to accommodate the condition, but this will not happen until the ECM achieves Closed Loop, engine warm. Until then, the ECM will employ the factory open loop fuel curve, which is generally rich by default. With fuel supply pressure operating at 20-30% higher than normal, the Open Loop fuel curve will be very rich. Depending on time to achieve Closed Loop, the cats could just warm up more quickly or sustain damage from overheating.

Next Steps:

1. Correct the fuel pressure fault, verify operating pressure is maintained at the specification you provide at idle, as well as under load (Torque Stall)

2. Do you have a scan tool capable of displaying real time engine data, specifically Long and Short term fuel trim? If so, reset the Long and Short term trim to establish a new baseline for the ECM to work from.

 

[DadOSix]

Fuel trim (time injector is open) is directly related to fuel supply pressure. If the pressure is higher than normal, more fuel will be injected over a given period of time.

The ECM adjusts fuel trim to accomodate component wear, but only to a point, and it is not instantaneous.

If your fuel supply pressure is siting at 60-65 psi, or 10-15 psi above the 49 psi specified pressure, the system will overfuel up to 20-30%.

The ECM will adjust short and long term fuel trim to accommodate the condition, but this will not happen until the ECM achieves Closed Loop, engine warm. Until then, the ECM will employ the factory open loop fuel curse, which is generally rich by default.

Thanks!

I understand that loop better now.

 

[Intermechanico]

2004 Jeep Liberty 3.7L w/ 183675 miles
Codes P0132 and P0152 (high Voltages at upstream O2 sensors both sides) Lean
Fuel Rail Pressure is 60 to 65psi at 750rpm idle. Online info states fuel rail pressure should be 49 +or- 5psi
Dealer tells me needed parts are obsolete and I need to replace complete fuel tank with upper and lower fuel pump assemblies.
I have already recently replaced; cats, O2 sensors, coils, injectors, lower Fuel Pump Assembly (twice)
I believe the Fuel Pressure regulator is the issue. It is housed in the upper assembly.
After market suppliers have pressure regulator on smaller tube on lower assembly.
I have tried two but believe the regulators are not to 49 psi spec.
No sign of vacuum leaks. I did not remove regulator in stock upper fuel assembly when trying the new lower assemblies.
I am considering putting a pressure reducer inline before the fuel rail.
Thoughts?

“2004 Jeep Liberty 3.7L w/ 183675 miles
Codes P0132 and P0152 (high Voltages at upstream O2 sensors both sides) Lean”

O2 Sensor Signal - High Voltage - generally means rich condition, not lean. O2 Sensor signal voltage operates as:

Lean Mixture - Lower than .5 volts
Rich Mixture - Higher than .5 volts
Stoichiometric - .5 volts

During normal conditions, Upstream O2 signal voltage will fluctuate constantly above and below .5 volts as the ECM adjusts fuel trim in real time, never remaining on either side of .5 volts for long

SUPPLEMENTAL: Google Gemini

P0132 / P0152 Thresholds: In the Chrysler JTEC/NGC engine controller, these codes don't trigger simply for being above 0.5V (a normal rich swing is 0.6V–0.9V). They set when the signal voltage gets pinned unusually high (typically above 0.99V to 1.1V+) for a calibrated window (usually 30–60+ seconds). Pointing out that the sensors are "pegged high" reinforces why the PCM flagged a circuit high/short code rather than just a routine rich mixture code like P0172/P0175.

 

[Intermechanico]

Also, there is a possibility that your fuel pressure is within spec at 60 psi. 2002-2003 spec is 49psi, while the spec changed in 2004 to 58 +/- 5 psi

 

[DadOSix]

“2004 Jeep Liberty 3.7L w/ 183675 miles
Codes P0132 and P0152 (high Voltages at upstream O2 sensors both sides) Lean”

O2 Sensor Signal - High Voltage - generally means rich condition, not lean. O2 Sensor signal voltage operates as:

Lean Mixture - Lower than .5 volts
Rich Mixture - Higher than .5 volts
Stoichiometric - .5 volts

During normal conditions, Upstream O2 signal voltage will fluctuate constantly above and below .5 volts as the ECM adjusts fuel trim in real time, never remaining on either side of .5 volts for long

SUPPLEMENTAL: Google Gemini

P0132 / P0152 Thresholds: In the Chrysler JTEC/NGC engine controller, these codes don't trigger simply for being above 0.5V (a normal rich swing is 0.6V–0.9V). They set when the signal voltage gets pinned unusually high (typically above 0.99V to 1.1V+) for a calibrated window (usually 30–60+ seconds). Pointing out that the sensors are "pegged high" reinforces why the PCM flagged a circuit high/short code rather than just a routine rich mixture code like P0172/P0175.

Execllent stuff! School appears to be in session!

 

[04Liberty#!]

Thanks for the input.
Attached are photos that may help
It most likely ran hot and with these and other codes for a long time. CAT and coil were definitely burn plugs and injectors filthy.
And when it would not pass emissions, it became my issue. It has been abused for sure.

I have focused on correcting rail pressure after cats, plugs, coils and injectors because all other codes went away after. And I read high rail pressure can cause the system to constantly self-correct causing the P0132 and P0152 codes. And it is easy to verify rail pressure. I figured get rid of these codes and see what happens next.

I do not have a real time scan tool but can probably get my hands on one.
To get the 49psi, I need a part, I cannot find. (see attachment). This is early 2004 so maybe 49psi is correct. If spec is higher why the codes?
Rail Pressure did come down when I did as explained in the attachment.

I will get my hand on a real time scanner and consider all Then let you know what I do and find.
If you have additional thoughts after looking at the attachment, please let me know.

Thanks for the help.
I want to get this little jeep in the mountains for some hunting.

 

[04Liberty#!]

Update:
Jeep was stalling when I gave it gas so I extended Fuel Gauge hose so I could see it from the driver's seat. It felt like low fuel pressure or air in the line. I suspect it may be due to the OEM FPR O-ring I removed. (as noted in previous attachment, Removing the O-ring allowed the new online PRV to work) But it has not stalled since i moved the gauge. OEM FPR is still in OEM UFPA without bottom O-ring and spring. Rail Pressure is holding steady at 55 over 600-4000 RPM range.

I have located a few same year & models at YPI close buy and will try to salvage some FPR & UFPA with 49psi setting. Otherwise, no luck on finding 49psi FPR or UFPA parts.

I checked new DriveBolt O2 sensors are in correct location by lead length. Short lead upstream. Long lead downstream? Only difference I could see. New Replacement 2292-03687545 Plugs/coil kit and TRQ injectors should be ok? New CATs might be sketchy but would be downstream O2 issue?

I barrowed my sons code reader. Attached is real time readings at idle. Looks like the PCM is pretty confused. It now running rough with a little light backfire. I need get more readings and graph overtime. B1&2 S1's are pegged could be fuel rail pressure or wire fault. Even with codes it ran better at 60psi rail pressure when OEM PRV o-ring and spring in place. As suggested, I think it best to get fuel rail pressure closer to 49psi before running it a bunch.

Thoughts?