I finally figured out how and where to mount my fuel prefilter this weekend. It is plumbed in before the stock filter. While I was at it, I decided to try an electric lift pump in the system temporarily. It is one of the solenoid type. Either the same or similar to the one GM used on some of the 6.2 or 6.5 motors if I remember right. This is not what I would use if I set this up permanently. A centrifugal type which wouldn't cause restriction if it failed would be my first choice, but I guess a check valve plumbed in parallel with any pump would provide an unrestricted source of fuel in the event of lift pump failure?

To make a long story short, the CRD ran just fine with a lift pump in the system. Couldn't tell any difference, certainly nothing negative. I don't remember the specs on this pump. I think it was something like 4.5 or 5 PSI. Don't remember anything about the volume it produces, but I know it was keeping up fine at idle, because I cracked the vent on the new filter head and fuel came out. I took the pump back out because it didn't have time to do the electrical properly, and don't want to use this pump permanently unless I decide the check valve in parallel would be a good fail-safe.

_________________
Anonymously tinkering with my CRD while protecting my warranty.
Ironically, if the warranty was worth having, I wouldn't have to tinker with it.

If you are using a pump for a 6.5TD, it is a flow through pump so if it does fail you will still get fuel. Their were 2 different sizes and the you have is the smaller on the 2. To see how well its keeping up just hook a pressure gauge up to the air bleeder on the OEM filter and open it up. These are not the greats up in the 6.5 but should do well in the CRD.

Greg

_________________
Greg
www.lubricationspecialist.com
888-306-4255

I seem to remember a post on this forum that indicated that the use of a lift pump for the CRD was in fact a bad thing to do. I can't remember the logic as to why this was the case and I don't have time right now to search the forum. Otherwise I would have installed a lift and a prefilter. Any information and/or support will be appreciated.

Doug

A Mopar expert on this board claimed that he'd seen it tried, and the pressure into the stock pump was too great, caused several different (apparently overfueling) issues. Here is the quote:

"A lift pump is very bad for these engines. It will severly throw off the calibration for the fuel and is not good for the CP3 high pressure pump as it already features a gear-driven low-side suction pump internally. Black smoke, severe misfiring, and horrid fuel use leading to the washing of the cylinder walls and dilution of the oil will result from its use. DO NOT use a lift pump on the VM engine in the KJ CRD. Just a warning as I've been through this trial-and-error before with them."

...and further...

"My experience with the lift pumps was with the engine on a dyno. I tried using pressures from 1psig up to 7-8psig and all had the same effects. What happens is that the internal gear pump on the CP3 delivers a certain pressure internally to the HP side of the CP3. By using a lift pump, you thus increase this pressure even more. The end result is that by having more pressure on the low-side, you throw off the calibration of the control of the HP metering unit (electric solenoid on the CP3). Additionally, force feeding the gear-driven suction is in no way approved by Bosch as per their documentation on the pumps.

How the Duramax owners solve this problem I am not sure as their CP3 pumps and EDC software are quite different. Based on what I saw, they only use it at certain times (i.e. WOT) where you want the extra fuel anyways if you're shooting for black-smoke performance.

In any case, not trying to stir people up, just trying to pass along my experiences and save you all the headaches on your daily driver."

Serendipity, I've had it on my list of things to do for some time to try this, since I just have a hard time believing that even a 1PSI pump made that much of a difference. You're a step ahead of me. But it wasn't clear whether you just tried it at idle or actually drove it for a bit. If I were you, I'd go ahead and hook up the lift pump temporarily, after warming up the engine, and drive it around the block a little. See if you have the symptoms described the MrMopar.

_________________
George Reiswig
2005 Jeep Liberty CRD
Suncoast, SEGR, lift, InMotion tune, homebrew B100
At 138k, new head & gasket, timing belt, rockers and swearing vocabulary

George,

I drove it about twenty miles at speeds from 5 to 75 MPH. No problems at all. Shut it off and restarted it 3 or 4 times.

_________________
Anonymously tinkering with my CRD while protecting my warranty.
Ironically, if the warranty was worth having, I wouldn't have to tinker with it.

OUTSTANDING!!!!

Good job!

_________________
Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler

I agree. This is good incentive for some of the rest of us to get off our duffs and try it out. Thanks for reporting on it.

_________________
George Reiswig
2005 Jeep Liberty CRD
Suncoast, SEGR, lift, InMotion tune, homebrew B100
At 138k, new head & gasket, timing belt, rockers and swearing vocabulary

I put in a question to Bosch in Germany for their feedback of the lift pump on the KJ CR-system since it has the low-side gear suction internal to the pump. It could be that the flow from the suction of the CP3 is exceeding that supplied by the lift pump you're using and so you won't see the same symptoms that I did with our dyno.

So if I read this right, the theory is that this particular lift pump has too low a flow to produce any real pressure prior to the CP3 suction pump? Your experience indicated that even 1PSI was too much.

I'll admit to being a bit skeptical about this theory...that seems like a pretty narrow sweet spot to hit, and given that the OP cited a pump around 4-5PSI designed for a larger engine (he was admittedly NOT firm on this), the chances of hitting that sweet spot seem slim to me. I know enough about engineers to think that perhaps Bosch doesn't want to say "I don't know" on this issue, or doesn't want to tacitly admit that they may not have a perfect design already, or they may be toeing the company line...or they may be exactly right.

MrMopar64, are you sure that there might not have been other variables in play that lead to the issues you reported? Serendipity, do you have any way of firming up the specs on the pump you used?

_________________
George Reiswig
2005 Jeep Liberty CRD
Suncoast, SEGR, lift, InMotion tune, homebrew B100
At 138k, new head & gasket, timing belt, rockers and swearing vocabulary

We have been using single and multiple lift pumps on the Duramax for a long time. People normally run 7-8 psi. The CP3 on the Dmax can take up to 15psi it my memory is correct. The more HP you want the more fuel that needs to be suppled to the CP3. With the pressure you are running it should be just fine.

Greg

_________________
Greg
www.lubricationspecialist.com
888-306-4255

The fuel pump we used is a MagnaFuel unit, set to 5psig at the CP3 inlet. With the pump on, the engine would smoke billowing clouds of black, run like crap, and be entirely instable. Shut the pump off, and it'd immediately go away. However, the CR-system on ours is a much newer generation (1800 bar, up to 6 injections) with the rail pressure control accomplished through use of both the CP3 metering unit and a PCV (pressure control valve) on the end of the rail, whereas the KJ uses just the metering unit on the CP3.

My main concern would be damage to the CP3 and/or metering unit from having head pressure against it when the system is not specified for it. Worst case scenario is accelerated wear of the pump and/or failure of the MeUn. I'll check with more knowledgable people from the supplier to get their take on it - seeing as how they have many variations of the CP3 both with and without the internal gear-drive suction, I'm guessing there's a reason why they didn't plan a lift pump.

Here's what I heard back from my DCX contacts:

The necessity of a lift pump on the KJ application is indicative of the following symptoms/issues:

*Low-pressure side air leak
*Failing ZP18 (the gear-driven internal lift pump)
*Clogged fuel filter resulting in not enough fuel delivery.

The presence of a lift pump can result in a pressure imbalance inside the pump and result in many issues.

After the fuel system has been primed and the vehicle runs without any air in the system, you should be able to press the primer on the fuel filter 4-5 times at which point it should get hard. If it doesn't, you'll need to start looking for air leaks. Remember that based on where you place the lift pump, you'll either suck more air in from the leak or force fuel out. The recommendation is to find the issue(s) and correct it as the lift pump isn't good in the long run for the pump, which as I'm sure is expensive to purchase and quite an endeavour to replace on the R2816 engine.

Just my feedback that I'm passing along...

According to my '05 FSM, that's incorrect. According to the FSM, page 14-86, the '05 CRD has a pressure control valve on the rail, called the Fuel Rail Solenoid Valve. It's described as a solenoid valve who's lift pressure is controlled by a varying current from the ECM to regulate pressure in the rail, along with the Fuel Quantity Solenoid on the injection pump, and has a corresponding fuel return line. And what's under the hood on my '05 matches the description and drawing.

From what I could find on Magnafuel units, those look to be positive displacement pumps, capable of supplying a several hundred HP engine. Have you tried a flow-thru or centrifugal pump, to see if you got the same results?

As far as the reply from DCX - I understand you're just the messenger, but also understand that for many of us at this point we're inclined to take any explanation from DCX with a grain of salt. For my part at least, after two years of this ongoing saga, if DCX told me that the sun was going to rise in the east, I'd be calling the National Weather Service to verify their claim.

_________________
Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler

Also on page 14-54 of the 06 manual it says the "cascade valve" located in the gear lift pump section of the CP-3 takes care of excess fuel pressure. You can also for a troubleshooting tool put some clear line in so air bubbles can be seen, a few tiny ones are normal. VW has always used a clear line between the filter and pump. If a clear piece were put in both before and after the filter unit it would help to determine where the air is entering. That way the real problem could be corrected. VW has proven a internal lift pump is all that's needed for normal conditions. A extermal lift pump will skirt the problem and I've used them on several 200,000 plus mile vw diesels but they were not expensive new vehicles. One could be used as a trouble shooting tool to pressurize the system with the engine off and possibly seep fuel out where the air is getting in. DC should really be working on this problem not us. But till the sun raises in the west we do what we need to do Come warm weather I'll seriously start tracking down my air leak

_________________
Atlantic Blue 06 CRD Limited (his)
Joined by a 2000 XJ Classic (hers)

I'd still be interested in knowing WHY Mopar64's test stand engine behaves as it does with a lift pump, not just a blanket statement from DCX saying "it just does, don't use a lift pump".

There has to be a valid engineering reason why his test engine behaves as it does. Is there some critical difference between his test stand setup and what's actually in the vehicle? Is it the type of lift pump they used? A physical design change in one of the components? A change in the ECM control software?

Figuring out why might not only help the young gent with his research, but help us avoid similar problems on the road.

It piques my interest when the same engine apparently runs fine with a lift pump in a real world vehicle, yet goes nuts on the test stand.

_________________
Mitchell Oates
'87 MB 300D Diamond Blue Metallic
'87 MB 300D - R.I.P. 12/08
'05 Sport CRD Stone White
Provent CCV Filter/AT2525 Muffler
Stanadyne 30 u/Cat 2 u Fuel Filters
Fumoto Drain/Fleetguard LF3487 Oil filter
V6 Airbox/Amsoil EAA Air Filter
Suncoast TC/Shift Kit/Aux Cooler
Kennedy Lift Pump/Return Fuel Cooler

MrMopar,

First off, I really appreciate you adding to these discussions. It is REALLY helpful to have someone who can contribute even a little bit of "inside knowledge." That said, I would respectfully suggest that you should include this level of detail (above) from the get-go, so that we understand that you were using a different fuel system with the lift pump. That would help a lot.

As for Bosch's input, I have to say that I know enough about engineers to know that they may be saying what they're saying due to
- not wanting to say "I don't know"
- wanting to cover their butts and not recommend an unknown
- toeing the company line
- an incomplete understanding of the issues CRD owners are facing regarding air leaks

Thanks for requesting this type of info from Bosch and D/C.

_________________
George Reiswig
2005 Jeep Liberty CRD
Suncoast, SEGR, lift, InMotion tune, homebrew B100
At 138k, new head & gasket, timing belt, rockers and swearing vocabulary

No harm in covering ones butt by using words like could, may, etc. Loop holes you know. My wife is forced to use them all the time. Just smart.

_________________
2006 Sport CRD

Could the Aztecs have known, that in 2012 after a 4 year experiment, our country would cease to exist?

Here is my thinking on this:

Why do we need a lift pump? We dont really...right? Its just a way of preventing air being sucked in through the fuel lines? (that is a question)

So we dont need 5PSI or even 1PSI for that matter we just need positive pressure in the line.

Could a person use a lift pump in combination with a fuel pressure regulator something like this
http://www.mooreparts.com/mm5/merchant. ... re_Code=MP

To keep the pressure low?

Or maybe this
http://cgi.ebay.com/ebaymotors/VW-WEBER ... dZViewItem


I still think I am going to put in an air seperator though.

_________________
It may be that your only purpose in life is to serve as a warning to others.

06 CRD Sport
Built 5/11/06
Jeep Green
Rocklizard diff cover
V6 Airbox

Why not just find the leak, and stop it up. Can only be coming from a small handfull of places.

_________________
2006 Sport CRD

Could the Aztecs have known, that in 2012 after a 4 year experiment, our country would cease to exist?

The advantage to having positive pressure is that the leaks come looking for you, instead of the other way around. I had a small air leak which produced no discernible symptoms until it produced a no start condition requiring bleeding (my wife was alone and she's not into bleeding fuel systems.) The other motivating factor is that I have plumbed in another fuel filter on the suction side of the OEM filter head and don't have a good way of purging all the air from it.

As to the specifics of the lift pump I'm using, I don't have them. I've owned this pump for something like ten years. If I remember correctly, it was a Lucas unit. I know I bought it from a diesel injection shop to feed a Stanadyne DB2.

I would need to put a pressure gauge in to determine pressure, volume is harder to determine, but not impossible. I am not done with this and will post further info when I have it.

I may look into just installing this as a primer, and not running it all the time. I'll give that some thought.

_________________
Anonymously tinkering with my CRD while protecting my warranty.
Ironically, if the warranty was worth having, I wouldn't have to tinker with it.