Takes 5 mins to pull the rail off the engine. Just be extra careful to not snap the plastic manifold. I twist that little fuel line where it joins if it is stuck (hasn't been removed lately) which "snaps" it loose to where it will rotate. Then I gently pull it off. Any side torsion on that plastic will likely break the cheap thing.

That's how I would make changing the solenoid really easy. Being that you only get one chance to seat that thing properly, I would be hesitant to try an in-place install.

But, if you opened the fuel rail completely (the line strait from the CP3), and you only get drops, then there is no high pressure pumping going in that direction, regardless of the position of the solenoid. You can get CP3's for cheap off of ebay, and they so rarely fail that I would be willing to bet that they are good (probably get a warranty from the big salvage yards).

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Mech fan, VH & AC delete

Don't EVER twist the fuel lines on that plastic return block - the real likelihood is that you will just twist the plastic nipple in half and trash the plastic block anyway.

As for the CP3 and the MPROP sensor... Sounds like the MPROP is what has failed on you. The CP3 should (by default) always be pushing at least some fuel to the rail, it is how I get the CRDs ready to start after working on them.

Good luck. If that doesn't fix it and you find yourself needing a known-good pump, let me know, I have one I can sell.

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Bad noises = REALLY bad things.

Thanks geordi, I will let you know. I am really hoping all I need to change is the MPROP. It is on its way from Oregon Fuel and should be here mid-week. Realistically I won't dive into the job until weekend.

And PS - I accidentally did break the plastic return block trying to get the small line from the injectors off. Interestingly the original design (AA suffix) has been discontinued. The new design (AB suffix) was around $80 online. I was able to find one of the original AA designs for $30 delivered, so I grabbed it. I don't know what the diff is between AA and AB, but for $50 more I am hoping AA will fit & work. It looks like the most difficult part will be getting the quick connect off the CP3 since the return block comes with that hose/pipe heat shrunk permanently onto the block.

Mountainman - I am changing the fuel quantity solenoid (or MPROP) which is on the CP3 pump. I am not changing the fuel pressure regulator on the end of the rail.

well is good news that you are getting close to find the problem , some time we do misdiagnose it but is part of the JEEP THING NOBODY UNDERSTAND) mountainman and I included thought you losing pressure but like you seen lately we seen MPROP valve problems , like our friend in the UK had , so we just giving ideas ,, happy new year to you and all crd lovers and their families.

I should have caught that when Flash mentioned the torx screws
hmm, there's a thread on the function of all of the CP3 parts. Would be cool if someone links that thread, or the part on the MPROP function. I hope that's the problem. The pulley on the CP3 takes a tremendous amount of pressure to remove it WITH the Miller tool. I don't know if any other puller will work.

_________________
05 CRD: H.D.S2 stat,WW Ironrock trilink&LCA's, OX rear,ARB front, 4.10's, ARB bumper, Suncoast,OME 3.5, JBA UCA,rock rails, Moabs&265/75 Duratracs, GDE tunes ,FFD fan,ARP's, 2 micron fuel, new valves,sasquatch battery tray & grid heater, tensioner relocated
Mech fan, VH & AC delete

Update. I decided to get started the MPROP replacement today, figured I could get a head start and at least get the old one out. The new one should be here mid-week. Couple of interesting things & questions.

First, does anyone know the exact operation of the MPROP? With no power applied I cannot look thru the cross drilled holes on the shaft of the MPROP. I can just barely see thru the edge of the holes. The ports appear to be open maybe a fraction of an inch. Maybe the shaft that controls flow is stuck partially open?

I know that with no power applied (and during cranking), the MPROP is not in operation and is supposed to let 100% of the fuel go into the high-pressure side of the pump and allow max pressure build. Then the ECM controls flow (and thus pressure build) by pulsing the MPROP and allowing fuel to flow back to the tank. It appears that fuel enters the end of the MPROP (the shaft is hollow) and is then directed either out the 4 cross drilled ports or is blocked off from flowing (anywhere?). But which fuel flow direction is to the high pressure side of the pump vs. back to the tank (through the cross drilled ports or blocked off)?

Also, once I got the MPROP out, I noticed what appears to be a new Bosch sticker on the pump. It appears to have a date code of 05-05-15. I will post the pic in a minute. Is that the way you guys would interpret this label? Is it possible that the previous owner had a new CP3 pump installed, in this case at the same time as the timing belt & water pump was replaced?

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I found this info over at oilburners.net regarding operation of the FCA (MPROP) -

[i][i]3. FCA fuel control actuator. It's job is to control the amount of fuel entering the low pressure side of your injector pump. It is a solnoid operated valve located on the bottom driver side of your pump. The ECM controls the action of this valve. Fully open and it has full fow of fuel into the High pressure side of the pump. closed and it will shut off the fuel supply..[/i][/i]


Can anyone confirm this is correct? If so, then I understand why my pump is not building any pressure. With the FCA/MPROP virtually shut, no fuel is being fed into the high pressure pump. It is all being directed back to the tank.

Since it's European made I'd bet the date code is in YY-MM-DD format.

_________________
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Since you are replacing the thing anyway... Might as well have some fun with it. How many pins on the connector? I don't know if it is a simple solenoid on/off or if it can open in stages, but might as well try tagging it with some voltage and see what happens.

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Over 225 CRDs currently driving with my valves, timing belt, rockers, or ARP Studs.
Bad noises = REALLY bad things.

The MPROP, while in the OFF state, is fully open. Sending all fuel up to the rail.
I know this because I can unplug my MPROP and the engine will still start and run. Although the ECU, sensing a critical fault, will force the engine to run in limp mode with reduced power.

The MPROP is just a simple solenoid in that it is either ON or OFF. However, the ECU uses pulse width modulation (PWM) to control exactly how long the solenoid stays on or off. This allows the solenoid to be in a position somewhere between fully open and fully closed.

The rail pressure solenoid behaves in a similar manner.
When in the OFF state the solenoid is fully open, sending all fuel out the return line and holding no pressure in the rail. This is why the engine wont start when the rail pressure solenoid is unplugged.
The ECU uses PWM to control the solenoid ON time, thus regulating pressure in the fuel rail.
The ECU relies on the rail pressure sensor to know how to control the rail pressure solenoid. If there is a fault in the rail pressure sensor, the ECU will force the solenoid to stay on and fully closed. The engine will run in limp mode and all rail pressure is regulated by the MPROP.

During normal operation the rail pressure solenoid and the MPROP work together to maintain optimal rail pressure and fuel flow.
By contrast, early 2.5/2.8 CRD engines and Duramax engines do not use a rail pressure solenoid. Instead, the fuel rail has a pressure relief valve that opens at about 28,000 psi. All rail pressure is controlled by the MPROP.

I learned this the hard way back in July when my engine was having rail pressure problems.

_________________
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I was doing some research on the net this morning and found some training material that sheds some light on the operation of the system. Interestingly the training material (see slides 16-19) indicates the FCA operates exactly opposite. That is - with no ECM signal only a small amount of fuel goes to the rail and with ECM power max fuel goes to the rail. The pictures in the training materials are exactly the FCA solenoid on our CP3 pumps. What do you guys think?

https://personel.omu.edu.tr/docs/ders_d ... 3_1913.pdf

I am unable to open that pdf for some reason.
But like I said, I can unplug my MPROP and the engine will start up and run. Therefore when off the MPROP is open.

_________________
U.S. Army Retired

Thanks much for the training file!!! Very good material to help understand how things work on our systems. Opened the PDF and saved it to my computer with the rest of my Jeep files for future reference...

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I played around with the old FCA solenoid. Can confirm the following, which appears to match what is outlined in the training material link in my earlier post -

1) With no voltage applied full flow thru FCA (confirmed with low pressure air into end of the solenoid)

2) With 12v applied, virtually no flow thru FCA

3) Mine appears to be working properly, at least now it is (see below)

What I cannot confirm is whether full flow (no voltage applied) is full flow to the high pressure side of the pump (like the shop manual indicates) or whether it is full flow back to the tank (like the training material from my earlier link indicates). This remains a point of disagreement depending on what you read/believe.

I do wonder if maybe mine was stuck. I was poking at it with a paperclip yesterday seeing how the spring & plunger moved inside. When I first started poking it was very stiff and the plunger did not seem to want to move. After fooling around with it for a while I was able to get to where if I pulled the spring the plunger would freely move back and forth if I shook it. In introspect I should have tried to flow air thru it and/or apply 12v before poking at it with the paperclip. Now I will never know if if was just stuck. At this point the new one will be here is a couple days. Planning to just install the new one.

Also, decided to install the carter lift pump as well. Seems like a wise thing to do regardless. So the tank is dropped, carpet is pulled up and new pump & connectors are on the way.

See, I'm a glutton for punishment, I'd have tried reinstalling the MPROP now to see if the truck will run again, and probably still replace it with the new one in a few days.

Chances are you found the glitch though - it was glued shut or the PWM annoyed it and it overheated in operation.

_________________
Proud supporting vendor of LOST Jeeps
TRAVELING CRD TECH. I come to you!
Need help? Just ask! I've taken it apart more than most.
Email jeep [at] maincomputer [dot] com - BOARD MESSAGING IS BROKEN
Over 225 CRDs currently driving with my valves, timing belt, rockers, or ARP Studs.
Bad noises = REALLY bad things.

Update. Got the lift pump installed. Bled the system. Now I know air in the system and/or fuel supply is not the issue, although I didn't think that was the issue anyway. The replacement FCA got delayed and isn't showing up until Mon. Warm here today so I decided to go ahead and try putting the old FCA back in just for the heck of it. Still no start. It was worth a shot.

But in my routing around I did find another interesting issue. To get better access to put the FCA back into the CP3, I pulled the aluminum cast bracket that goes between the alternator and intake manifold off. Its just 3 bolts. I found that several wires in the bundle that routes behind the bracket had worn through thru and were arcing (clearly visible brown arc tracks). I will post pics in a min. But this got me to wondering if this arching might have caused (or is still causing) my issue. Does anyone recognize what these wires might go to based on color? I have checked every fuse on the left side of the IP and under the hood in the main fuse block in front of the battery. Nothing is blown. Are there any other fuses or fusible links hidden somewhere? Any thoughts on whether the arcing might have damaged the ECM?

Pics next -

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Another note. The ECM claims there is still virtually no rail pressure - same as before. I did pull the injector returns off all 4 injectors just to see if anything was flowing out during cranking. Nothing. There is fuel down in the injectors, I can see it. But nothing is flowing out the top/return during cranking. I am getting some light smoke out the tailpipe during cranking which seems odd since I don't believe the injectors are getting enough fuel/pressure to fire.