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 Post subject: Low fuel rail pressure
PostPosted: Tue May 22, 2018 12:15 pm 
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Joined: Sun Mar 30, 2014 9:53 am
Posts: 297
I need some help.
The check engine light in our 2006 CRD came on and at the same time, the Jeep experienced reduced power. I think it went to limp mode. I pulled the codes and found P0093 (FUEL RAIL PRESSURE MALFUNCTION POSITIVE PRESSURE DEVIATION) and P0203 (CYLINDER 3-INJECTOR). My wife said the last time she refueled, the tank was very slow to fill. I replaced the CRD fuel filter thinking the diesel she purchased may have some trash in it. While I was under the hood, I checked the wires to #3 injector. I found the insulation was worn through one conductor where it exists the plastic cable tray on top of the engine. I saw no indication of it shorting to ground or shorting to any other wires. I re-taped and repositioned the injector wires. I cleared the codes and went for a drive. After about a 1/2 mile, the check engine light returned. I pulled the codes and found P0093.

I pulled the #3 injector and had it tested. The shop told me it was good. I re-installed the injector. Restarted the Jeep and it behaved as before. Started and idled without a check engine light. During test run, check engine light came on.

In attempt to repair it, I did the following:
    Replaced Fuel Filter (Racor - 2 micron)
    Confirmed in tank lift pump works
    Jeep started and idled with no check engine light. During test run, check engine light came on.

    Pulled, tested and re-installed #3 injector
    Jeep started and idled with no check engine light. During test run, check engine light came on.

    Replaced Fuel Rail Solenoid
    Jeep started and idled with no check engine light. During test run, check engine light came on.

    Replaced Fuel Rail Pressure Sensor
    Jeep started and idled with no check engine light. Engine died while backing out of driveway and would not restart.

    Replaced Fuel Pressure Regulator on back of CP3
    Jeep will not start

Checked fuel rail pressure with Torque Pro ~ 160 psig.

Does anyone have any ideas?

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2006 CRD Sport
GDE FT ECO tune, GDE TCM ECO tune, ARP studs, HDS-001 203F T-Stat, 3.7L nylon fan & Hayden 2905 clutch, Carter P76148M in-tank pump, Racor 245R122 filter head & 2 micron R25S fuel filter, Provent 200, Samcos, Fumoto F-102, Litens 920834A de-coupler, PML rear diff cover, OEM trans pan with welded in bung, JBA UCAs, full skids.


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 Post subject: Re: Low fuel rail pressure
PostPosted: Tue May 22, 2018 3:00 pm 
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Location: Prescott, Arizona
Is that pressure while cranking? If so, it is WAY low. The rail needs to be somewhere in the 2000 to 2500 psi range for the injectors to even open. It is possible that the fuel rail pressure sensor is bad and the replacement is either bad or not installed correctly. I seem to remember it requires a bit of a funny installation procedure? I haven't done one personally, so maybe someone else can help there. In either case, your ECU is not receiving the proper signal from the rail so you're on the right path.

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2006 Limited CRD: Frankenlift II, Fumoto Drain Plug, DIY Stage 1 Tune, In-Tank Lift Pump


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 Post subject: Re: Low fuel rail pressure
PostPosted: Tue May 22, 2018 9:01 pm 
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Gorden on here is the expert on the fuel rail and it's associated sensors.
Hopefully he will chime in and share his expertise with you.... :roll:

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05 Jeep Liberty CRD Limited :JEEPIN:
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 Post subject: Re: Low fuel rail pressure
PostPosted: Tue May 22, 2018 11:27 pm 
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Location: Oregon Coast Dairy Country. Land of stumps, dumps, and "Liquid Pumps"
Not an expert. Just had to dissect very nearly the entire system to troubleshoot an electrical problem caused a mechanic shop who was in way over their heads.

anyhow

I see you have an in-tank pump. That is good, and I assume you have checked that it is operating properly.

I'm thinking the #3 injector thing is some kind of random feedback from the fuel pressure issue. OR perhaps within the wiring loom there is a short between the #3 injector control wires, and the fuel pressure circuitry. 12 years of diesel vibrations cause all kinds of nasty things to happen to wire insulation that is also subject to high heat. Easy enough to sort out with a VOA meter and repair.

The Fuel Pressure Sensor, mounted very near middle of the rail, with 3 wire connector is the Eyes and Ears of the ECM, and continuously sending data to the ECM, which monitors and uses this data to send PWM voltage orders to the Fuel Quantity Solenoid (CP3), and the Fuel Pressure Solenoid (rear of Common Rail) to manage how much fuel enters the fuel rail, and how much fuel is bled out the back end of the fuel rail, to accomplish what hydraulic pressure the ECM wants at that exact particular instant. Any deviation (beyond normal parameters) from what the ECM expects to "see" results in Diagnostic Trouble Code set, and Limp Home Mode. Any goop or burr or something that causes the solenoid valves to stick, even for a millisecond, will also result in the same situation. If the communication between the ECM and Fuel Pressure Sensor is interrupted or erratic, It seems to slip into a "panic mode" where timing and quantity result in enormous clouds of black smoke even at moderate rpm.

The Fuel Quantity Solenoid on the CP3 functions essentially like a flow valve on a hose, and through PWM voltage from ECM, regulates flow to the HP pistons. Voltage increase closes flow. Voltage decrease increases flow to wide open maximum. Any voltage interruption in this control circuit is "fail-safe", as in the engine goes into Limp Home Mode, but can continue to run, but badly. All pressure regulation duties are now up to the Fuel Pressure Solenoid, who attempts to regulate through bleed-off.

The Fuel Pressure Solenoid on the Fuel Rail functions essentially to bleed off precise excess fuel, to establish the maximum fuel pressure in the rail. PWM Voltage from the ECM regulates, as voltage increases, rail pressure increases. When voltage decreases, rail pressure ceiling decreases. Any voltage interruption in this control circuit results in instant die, and no start condition, as there is no bleed-off pressure safety to keep pressures from spiking and damaging rail or injectors.

My bet is a problem with the wiring or connectors. Somewhere, one (or more) of these 3 has a communication problem.

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 Post subject: Re: Low fuel rail pressure
PostPosted: Wed May 23, 2018 5:36 am 
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After replacing both the rail pressure sensor and fuel quantity solenoid, and still having problems, I replaced the harness connectors for both and the problems went away.

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 Post subject: Re: Low fuel rail pressure
PostPosted: Wed May 23, 2018 9:24 am 
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Location: Central GA
GordnadoCRD wrote:
Not an expert. Just had to dissect very nearly the entire system to troubleshoot an electrical problem caused a mechanic shop who was in way over their heads.

In my book that makes you one of the most knowledgeable persons around i.e. "expert" or whatever you want to call it on matters of fuel rail issues and its associated pressure control sensors... :mrgreen:
Wear your label with pride, you earned it! :wink:

:SOMBRERO:

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Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited :JEEPIN:
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount

98 Dodge Cummins 24 Valve


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 Post subject: Re: Low fuel rail pressure
PostPosted: Thu Feb 07, 2019 8:54 pm 
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Joined: Fri Apr 01, 2011 7:12 pm
Posts: 21
Location: Volcano, Hawaii
My system trips the p1202 after reaching 3000 rpms. Did you experience this also?

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 Post subject: Re: Low fuel rail pressure
PostPosted: Fri Feb 08, 2019 12:42 am 
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Location: Boise, Idaho
Check the fuel rail solenoid pins at the ECU. You may find one of them discolored. Scrub it and put dielectric on it and give it a minute, like 1 degree bend for better contact. I've fixed 2 CRD's this way

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Mech fan, VH & AC delete


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