A intermittent fuel rail pressure problem was driving me nuts and I couldn't figure out the problem. So I ordered this AutoMeter fuel rail pressure gauge to help me diagnose the problem. It wires in directly to the wire harness connector on the fuel rail pressure sensor.
Two wires go to the sensor.
A long purple wire connects to the sensor signal wire, middle wire on the connector.
A long black wire connects to the sensor ground, yellow with brown stripe wire on the connector.
The shorter black wire goes to a good ground along with the black wire from the gauge bulb.
The shorter red wire goes to a fused key-on terminal. I chose the radio fuse.
The white wire from the gauge bulb can go to any key-on terminal but chose to connect it to the fuse for the instrument cluster lights.

During the process of figuring out the best way to wire in the gauge I discovered a intermittent open circuit in the fuel rail pressure sensor. So I replaced that connector which seems to have cured all my problems.
The connector is pretty common on many makes on models. I got mine from a local Chevy dealer. A Chevy duramax uses the same sensor a our CRD. Online prices are about 20-30 dollars.

When wiring in the gauge it is best to solder your connections at the sensor and seal with shrink tube. A loose or corroded connection can cause you some serious problems down the road.

Glowshift offers a similar gauge that has both analog and digital displays. Available on Amazon for about $100.

This gauge is not really a necessity for every day driving but can be a great tool for diagnosing fuel rail pressure problems.





Comparing the pressure gauge to rail pressure readings on the TorquePro android app:
When using TorquePro, the displayed rail pressure is what is demanded from the ECM and correlates to the position of the fuel rail pressure solenoid.
The AutoMeter gauge displays actual rail pressure from the sensor.
The AutoMeter gauge reading can be 500-2000 psi greater than what is displayed on TorquePro and is a more accurate representation of how well the injection pump is working.
Remember, there are two ways the ECM regulates fuel rail pressure.
1. The pressure control valve (PCV) solenoid on the fuel rail.
2. The fuel quantity solenoid (MPROP) on the CP3 injection pump.

With a fully warmed up engine. At idle, fuel rail pressure readings are:
Gauge- about 5400 psi.
TorquePro- about 4900 psi

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U.S. Army Retired

Thanks. For the detailed install write up. I may need to do this.

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2005 KJ CRD 114k miles
GDE Hot
GDE TCM
ORM -cat, muffler
4" lift, locking diff, a-arms
ARB bumper and warn winch
Electric Radiator Fan
Hot Wheel turbo
Fresh Rebuild after near death head gasket coolant leak
Lift Pump



Located in The Gorge Oregon

Awesome, you should move this in the tech section flash. I will probably end up adding one, my initial thoughts were to use the probe also, which is quite a pain due to those thousands psi. Good write-up, thanks!

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2005 kj CRD, samco, suncoast tc, provent, Kennedy lift pump, GDE ECO full torque, 2nd gen filter head, 245/70/16 a/t tires, mopar light bar, fumoto oil valve, OEM Skid Plates, ARB Front bumper and HD OME, tru cool LPD47391 40k GVW tranny cooler (stock cooler delete), FF Dynamics e-fan and shroud, rocker arms replaced, HDS2 190F thermostat.

flash,

How much fluctuation do you see on the TorquePro at idle? Mine is fluctuating between about 4600 and 5000 psi at about 760 rpm. My Glow Shift gauge is reading a steady 5400 psi. My rail pressure sensor connector seems tight. I've been chasing the P0093 for a long time and have done and checked everything mentioned on this forum except the PCV and CP3. Like you, I'm reluctant to spend more time and money without some diagnostics.

~Gary

Your pressure gauge reading looks good.
Your TorquePro pressure reading seems normal for a engine with the A/C on.
Does it change with the AC off?

With the engine idling and observing rail pressure on TorquePro, wiggle the rail pressure sensor harness conector.
If you see pressure spikes up to 25000 psi, the harness connector needs to be replaced.

Also, try unplugging the MPROP on the CP3. This will induce limp mode.
Watch your pressure readings while idling and driving to see if that make any difference.

_________________
U.S. Army Retired

Just stumbled on this. Do you know if we need the gauge for the 03-07 cummins/GM LB7 or the 07.5+ Cummins/GM LBZ?

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

Hmmm... I dont recall there being an option.
Heck, I dont even remember where I ordered mine from.

I'd go with the early model duramax because our CRD uses the same rail pressure sensor.

_________________
U.S. Army Retired