so precursor:
i had running issues, checked rockers changed cambelt and aux. had all 4 injectors reconned & new fuel filter housing and filter.. this cured the rough acceleration and rocking engine when revved.

driven 200mi since. yesterday I started the car and left to idle for less than 2 minutes, came back and it had stalled. will not restart. checked fuel supply, and also tried to run off a bottle. still no start at best a cough, stumble but thats it. no fuel is being returned out of the back of the fuel rail.

I think the fuel quantity valve may be stuck? If i disconnect the power from the back of the valve MPROP FQV what ever you call it, it starts to fire immediately then stalls out (prob a saftey feature?) if reconnected it will again crank but no fire...

It is due to Jeep tomorrow for key coding but it aint goin nowheres fast!!!

FIXED
It was the 'MPROP' 'FCA' 'FPR' valve on the Fuel pump. I replaced it with a spare after much chin scratching and it fired first time.. For those in the UK looking for cheap replacement parts it is common with the LDV Maxus and Chrysler Voyager. m(Same 2.5 / 2.8 CRD) the CP3 pump is also fitted to may renault DCI's so this MAY be interchangeable / worth a shot if cheap or you have one lying around.

when start and die , you see a fuel in the return line ? can be the regulator on top of the fuel rail that has failed open and your rail stay empty

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that has been checked and no fuel flow so rail reguator is fine.

interestingly I just got it started. If i remove the connector to mprop start (then stall) then reconnect etc a few times it will spring into life run and drive no problem. as soon as i shut it off then no start again...

so either playing with the MPROP is changing the rail pressure somehow or applying some on/off to the sticky mprop valve?

it would seem that in my mind - connector removed creates more pressure than connected but with no control so ecu shuts it off? if so why would it not just work with connector connected?

hopefully a pump guru is here somewhere..

I dont know what year/model of CRD you have but...

On my US spec 2005 model, when the MPROP is unplugged all fuel is sent up to the rail and none is returned from the pump. All rail pressure is controlled by the solenoid on the fuel rail and excess fuel is returned from the rail. In this condition the engine will run but will be in limp mode.
Some euro spec models do not have a rail pressure solenoid. They only have a rail pressure relief valve that opens at about 26,000 psi.

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U.S. Army Retired

I have a rail mounted sensor i guess is a rail pressure solenoid? half way down the rail, 3 wires connected?

so with valve disconnected I get instant fire then instant stop. which would mean max pressure. then ecm stall maybe. so if it were sticking open a bit then i would loose rail pressure. if however it fires with power disconnected then you imagine it would be fully shut? i.e not stuck.? certainly seemed to work better if plugged on and off a few times maybe jiggling the shaft.

anyone know the bosch part number for this valve??

EDIT- ok i hvae just read that the valve holds closed on a spring, and the electric coil applys more pressure to increase rail pressure or less to reduce.

If it were a weak spring then starting could be a problem, or a stuck component modulated by the coil in an attempt to increase pressure and infact due to its modulation actively be reducing pressure? hence cycling it on/off would alow rail pressure to increase and give a disconect reset to the valve.

i have found 0 928 400 505 bosch looks like the part from the back.?

or bosch 0928400738 from 2.8crd but states KK model not kj?

The rail pressure sensor is half way down the rail with three wires.
At the end of the fuel rail, up against the firewall, will be a valve.
If there are two wires going into that valve, its a rail pressure solenoid.
If there are no wires going into that valve, its just a pressure relief valve.
I think what ypu have is just a relief valve.

Here is what I think is happening to yours:
1. With the MPROP unplugged, all fuel is being sent up to the rail a max pressure.
2. With the MPROP unplugged, the ECU has zero control of rail pressure.
3. The pressure relief valve is doing its job. Relieving all pressure in the rail to save the CP3 and injectors and causing the engine to stall.

If you plug the MPROP back in before the engine stalls, the ECU regains control of rail pressure, allowing the engine to run normally for a short peroid of time.

I suspect that you have a intermittent wiring problem with either the rail pressure sensor or the MPROP.
I have dealt with both on mine.

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U.S. Army Retired

Hmm ok.

Mine is as you say with no wires to the rear of the rail no solenoid. if it were a intermittent wiring fault it would stall while driving etc? I have driven it out and about once running and it drove normally. but as soon as its turned off it will not start with the MPROP connected. it is stumbling more now. than it was. arrgh.

if it is a wiring issue what were your faulty items? or likely places to look? gonna look at the KJ manual online and see what it says. I had no CEL light up until i removed the mprop valve.


Going back to basics: common no start problems
Cam sensor -
Crank sensor -
air in fuel - checked and verified by start with connector disconnected
fuel rail pressure relief valve leaking. - Verified no fuel leaking on cranking

so for Dash indication does cam sensor reads RPM or crank? would it run if MPROP were disconnected and it had no signal from either sensor?

Less common:
CP3 Pump failure
CP3 Metering valve failure

For mine, after a lengthy diagnostic process, it was the harness connector at the rail pressure sensor.
And then later, after similar problems, I replaced the harness connector at the MPROP.

connector part numbers:
ACdelco PT2050 rail pressure sensor
ACdelco PT2183 mprop

Another possibility is that the problem is the pressure relief valve.
This seems unlikely but its not impossible.
I dont know the part number for yours but I know that DuraxMax and Cummins engines use a similar valve.
Some Duramax and Cummins owners have removed that relief valve and replaced it with a solid plug.
It can be found here: http://sinisterdiesel.com/i-15883633-sinister-diesel-fuel-rail-plug-race-valve.html?gclid=CND37bCck8kCFdUvgQod_DUFLw

In any case, diagnosing a fuel rail pressure problem can be very difficult without a gauge.

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U.S. Army Retired

thanks for the info. I'll have a look at the connectors.

The prv (at the end of the fuel rail right?) is not letting and diesel out when cranking. if the rail pressure sensor was faulty could it also cause this problem?

If the rail pressure sensor was giving a false HIGH signal to the ECU then the ECU would try to regulate the MPROP to reduce rail pressure.

Try disconnecting the pressure sensor to see if that effects engine start and run. But have the mprop plugged in when you do.

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U.S. Army Retired

i have a feeling that the engine wouldn't fire on this export model with that sensor disconnected?. hell I'll give it a try

Just working my way through this..
http://oregonfuelinjection.com/pdf/jeep ... nostic.pdf

i say replace MPROP valve anyway its 10 years old ,,, this thing is getting old may not be the problem (no codes ) but its a good starting point

this car has cost me so much already, in time and cost. It exists on a knife edge. I keep putting it right and it still fudges about. everything is 'this is the last thing now, it will run fine for another 100k...' except i get 1-200 miles. GRRrrr.

anyone know the exact part numbers for the MPROP.

i know , once you get hooked with this car is no way back , i grew up in south eastern europe , and my dad drove Fiat, cars , we always cary spare parts , every trip , axle joints, clutch cable , ignition related parts , belts .this car is no different , but we like it so we have to fix it. again its really nice hobby car and keep us busy , makes me drink more beer , i don't know i can't explained for sure this car falls into a "special category''

Well, I know that on my engine it will run with the pressure sensor unplugged. It will be in limp mode but it will run.

The fact that you can make the engine run by unplugging the mprop tells me that its good.
The mprop is just a solenoid. Its either ON or its OFF.
When OFF, the majority of the fuel is sent through the pump and up to the rail.
When ON, the majority or the fuel goes out the return line.
Then ECU cycles the mprop on and off to regulate how much fuel gets sent up to rail.
The ECU uses the signal from the pressure sensor to determine how much regulation is required.

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U.S. Army Retired

OK. removed connector and no change still no start. been back and revisited the rail pressure relief valve and as discussed; with the MPROP disconnected it does open and stall the car you can hear it click and pulse fuel.

So - we can make pressure for sure. the connector to the pressure sensor looks in very good condition.

does anyone know what voltage should be on the reference wire of the pressure sensor at atmospheric?

what else could command the ECU to open the MPROP?

normally the valve on top the fuel rail is closed for the 1st 30 second for achive the desired rail pressure for start the engine that must be 430 bar if I don't remember wrong , unplugging the MRPROP I think you reach the desired pressure but if the regulator leak the engine do not have the right fuel quantity , normally a non start is the valve on the top of the fuel rail that leak .
after a shut down this vale must close , but if they leak the fuel rail is empty and at the next cranck you can't reach the desired pressure for starting the engine .
a faulty MRPROP can cause a limp mode in a WOT because you can't reach the desired pressure of 1600 bar with a proper code in the ecu P0093 or P0087 if I don't remember wrong

do this , with a diagnosis read the fuel pressure at key on and during cranking if you do not reach the 430 bar at 99% is the regulator on the top of the fuel rail
or worse a fuel injector that leak from the return line
my 2 cent

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ECU Tuner -EGR OFF -DPF OFF Swirl/Flap OFF, Lambda OFF , DTC OFF in many cars , not ONLY

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so tested fuel rail sensor 0.5v output at key on. (this is spec) gnd and 5v+ are present

metering valve is humming at key on is this normal? if i disconnect the rail pressure sensor the humming gets louder.

Which one is the metering valve?

When I was working through my fuel rail pressure problems, I discovered that when the engine was idling and I wiggled the wires to the pressure sensor the engine would stumble and sputter like it was going to die. Thats how I determined that the problem was the wiring and not the sensor.

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U.S. Army Retired

sorry it has so many names - mprop

it has 12v to one side and the other wire reads 115k ohms through ecu, and open circuit to earth when ecu loom disconnected so the wiring checks out.. i think