CP3 Is Leaking
 

So I suppose the only remedy is to replace the entire unit. Or is there another way?

Where's the leak, or is it just bleeding down and not holding pressure?

I was underneath and found a wiring harness and the underside of the CP3 damp w/ fuel. Lucky it hasn't made it into the oil, or at least I don't think it has. Oil level stays the same.

So its leaking where the wiring harness comes out of the pump? That's actually pretty minor and there should be a replacement seal available. There is no high pressure at that location so some small leakage really isn't much of a problem. I'm willing to bet that most of em leak there a little.

Kinda hard to tell. Looked over the top and looked a little damp there also.

this is probably your hard start issue all together!

Hell I just saw this thread and thought the same thing

Yep, you're sucking air. Maybe one of our nice vendors will check on a seal kit available. :w2: And don't freak out over doing an overhaul. Its not a difficult as you might think. :up2:

I hope I'm not causing damage. Might be why it's not idling as smooth. Maybe.

Yup thats your rough idle and hard start! no , Your not causing any damage!

I'll round you up some part prices tommorow!

Yeah, what he said. You're not causing any damage just a thorn in you side that will get worse. It's probably causing issues while highway driving that aren't real profound. Rail pressure will surely be down at cruising speeds.

Heck fellas, I'd give you all a big bear hug if I could, but I suppose a thank you maybe sufficient enough. Thanks a bunch!

There are two write-up's here on how to rebuild and mod the CP3. One is in the DMAX section and the other is in the Cummins section. They are sticky's so they're easy to find. Its not that tough to do. :up2:

A leaking CP-3 rarely is the cause of hard starts. They don't suck air and usually only seep becuase of the expansion rate differences in th epump pieces. The pump leaks in cold weather and usually quits in the summer. If it is the pump you will see other performance problems also.

Mine leaks every winter and have had no starting problems.

mine is leaking in the same place with a little fuel in the wires below it. Minehas had a hard start problem for a while now. Could that leaking and losing its pressure not be playing a large role in the hard starting problem? Thanks for posting it!

This can be true in some cases but not in all! Theres a good possibility that this one is leaking on the inlet side, Causing the fuel system to loose prime. This has already been discussed in another thread!:U:

The situation you describe can never happen. The intake side of the CP-3 does not draw and cannot introduce air or lose prime as it is pressurized 7-9 psi from the LP. If there was ANY leak large enough to introduce air you would have a constant stream of diesel showing not a seep. In addition, you cannot introduce air to a pressurized system unless the air pressure is greater than the internal pressure.

A seeping CP-3 is normal in the cold months due to the design of the pump, aluminum mated to cast iron has different expansion rates and the o-ring tolerances are too small to contain it.

Long cranks and hard starts can be a trashed pump or other problems in the fuel system but a seeping pump is NOT a sure indication of the problem.

I made an orginal post, Then thought this shouldnt be a peeing match. You entitled to your opinion and so am i!

We all understand these pumps are fed from a lift pump. That DOES not mean that you can loose a prime in the system. for instance, create a leak in a line and see what happens in a fed system!

Again ,We're all here to help, not squable. So lets help get this guys truck running!

What pissin' contest? I pointed out an obvious flaw in your thinking and I see no where in my posts that I have been disrespectful or flippant about your opinions? :3:

In fact, your whole attitude indicates your opinion is more valid than mine and you feel the need to make this into anything more than a discussion. :booo: If you really want to help read on and I will explain why your theory has so many holes in it. :pca1:

You talk about losing prime, but it doesn't and can't apply here. The systems, both low pressure and high pressure are PRESSURE fed. How would a leak impact this? Any air in the system is going to compress as the pressure is applied. The only symptom you might see is a slight stumble on the initial ignition. I invite you introduce a leak into a pressurized system and see what impact it has and the results. There will be zero impact on the running portion and a mess from all the fuel sprayed out. I see no where then original poster has indicated massive fuels leaks that would result from this kind of leak.

You need to understand a couple other things also. Both the low pressure and high pressure systems are self priming and will bleed any accumulated air as soon as they are energized. This is done becuase entrained air in diesel is a fact of life and while the system is not functioning air will accumulate at the highest points, chiefly the filter, the CP-3, and the rail. Why do you think the wait to start light does not go out immediately when there is no need for gride heaters? The low pressure system runs the fuel pump until it sees nominal pressure. This will compress any air and force fuel under pressure to the gearotor pump in the CP-3, at the same time the FCA opens to return flow to bleed air and fuel out. Concurrent with the low pressure side priming, injecors 1 & 6 start cycling to bleed off any accumulated pressure in the rail and provide a prime path as soon as the CP-3 starts delivering pressure. There is a reason a minimum of cycles engine revolutions before a CR engine will fire. It is not only synching the cam and crank sensor but purging the fuel system so when it says FIRE, it starts. This is straight from the FSM, Bosch specs, and conversations with techs and engineers.

Personally, I have had 2 pumps leak and never a hard start issue. I have seen literally hundreds of the same issue posted on multiple boards for the the last 6 years and less than 5% were a pump issue. I will say it again, A SEEPING CP-3 IS RARELY THE CAUSE OF LONG STARTING ISSUES. As long as its not making oil and not leaking large patches of diesel under the truck, there are cheaper and higher percentage causes to be investigated. I posted those items on the other thread.

Thats my opinion backed up by experience with easily checked references.

My 02 LB7 had a leaking CP3 and it caused hard starting and rough idle. Repaired the CP3 leaks and the problem went away.
As for the dissimilar metals, they are put through the proper heat treat process to maintain tolerance so there is never to be any leakage. Both metals will expand and contract at the same rate until the alloy reaches -60*F. At that point the aluminum will contract at a slightly faster rate then a 4130 or 4140 with Rockwell C.
And I do stand corrected on the "sucking air". I should been ashamed of myself for saying such. What is really happening is loss of positive displacement.

This wont be tolerated.

PLEASE READ....
https://www.dieselbombers.com/specif...les-101-a.html

Just on the outside looking in-

IIRC the Duramax didn't have a lift pump in the trucks until 2005 or so but the Dodges with a CP3 have always had a lift pump.

So maybe the lift pump is the reason you guys have different results? Maybe the earlier Duramax trucks could have this issues cause a no start because they didn't have the lift pump to force feed the fuel?

The Duramax has never had a factory lift pump.

You just cant say a fuel leak EVEN on a PRESSURIZED SYSTEM wont effect starting. None of us will ever know everything.
He is correct on a few things, I'm not trying to say he's not. I know for a fact, EVEN on a CP3 system with a pump that if the factory lift pump is week it can allow fuel to back flow!

The tank is lower than the pump, It can and will siphon back and cause a hard start issue!

He's also right that most pumps will seep a little fuel , But much more than a seep is a concern. I was under the understanding it was a decent size leak!

The Duramax DRAWS fuel from the tank, it is not pressure fed. Small leaks do not impact a pressure system like they do one relying on a vacuum to draw the liquid. The Cummins application is, and always has been, pressurized thru smaller lines.

I agree the expansion rates should not make a difference but that is obviously is what is happening with the pump. How else would explain leaking only in the colder months and none when ambient tempos remain above 60 degrees or so? How do explain resealing the pump with larger diameter o-rings will in most cases eliminate and others considerably slow the leakage?

Its the temp difference from ambient to operating that I see causing the leaks. If you have another theory please contribute.

There are a couple people in here that need to respect the opinions of others. If you disagree you need to keep it civil. A link to the rules has already been posted in this thread and you might want to read it.

I'm quite well aware of that. Re-read my post #23. However, my trucks ARE pressure fed.

The metals are not getting out of tolerance. Replacing the O-rings with larger units isnt the answer either. If a 70 durometer HNBR seal's and o-rings were used we wouldnt see this issue. They got cheap on the material.


This thread is being pulled way off course. I would be glad to discuss the design and Engineering of the CP3 with anyone in pm's, chat or even another thread but not here. Lets move on to help fix wildbill's problem and take up any Engineering or Technical discussion somewhere else.

First, let me aplogize for the inadevertent words that seem to be upsetting people.

I called NO PERSON out or any way shape or form denigrated their opinon.

The statement was example only that I am direct in my statements. If I think you are wrong I WILL call you on it but nicely. I will also provide an alternate theory and explain why I think your wrong. If you don't like discussion and a certain amount of dissension then these forums are the wrong place to be. :)

DangerousDuramax, I pointedly disagree with your contention this thread is going off track. Its now ON track because I pointed a few holes in the theories. You cannot compare the Duramax systems to the Dodge systems. They are totally different and have their own little quirks. I saw this thread headed down a dead end road becuase I HAVE BEEN THERE! Isn't that what these discussions are for? I am simply sharing my experiences and what I have found thru experience.

Furthermore, DangerousDuramax, look at your own attitude before offering me any advice. Where do you derive authority to decide what is on or off track? Get over yourself. You have the same capacity to be wrong as the rest of us and wanting to drop ANY discussion that contradicts your opinions makes you look a little closed minded. (Moderator delete if you must but take into account there is a least one left here that wants a fight rather than dialog. I have no problem either way)

Thanks for your Opinions !

And yes its never meant to be construed that staff is here to tell anyone whats right and wrong , its our Duty to the site to Try to keep it Moving Forwards and Productive in a manner in which others would like to join in .

Calling blaspheme dont make anyone happy for sure , And like tracy said we really do want to her about your experiences with the topic and feel free to share in a manner in which your not dogging others if possible

No ones right 100% of the time , Whats right is facts gained from personal experiences ...Do Share

DM

Must be Monday!

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Not sure if it was the 36 deg. this morning, or it being plugged in but it started and idled much smoother. I reprogrammed Smarty to moderate torque and when it told me to unplug I waited 15 sec. then another 15 sec. after I unplugged it. So we'll see what happens in the next few days.

dang ive missed all the fun lol lol


:pca1:

lol

Nope, you're just in time. :)

Update. Crawled under the truck, pump is covered head to toe w/ fuel. Got a drip thing going to.

Atleast you found the problem

Replace entire pump, or just a simple gasket replace?

Here is a list and source for the pump seals that will generally stop the leaks. Mixed results though. Some have reported no more leaks while others had them return in cold weather. The other choice is replace the pump with a Stage 1, maybe?


Philadelphia Ball & Bearing Co.
1346 Centre Avenue
Reading PA.19601-1412
phone # 610-376-7500


1- 25x36x7 harwal seal this is stock size
1-25x37x7 harwal seal this is stock size
1-2.50x54.00 ame o-ring this is 1mm thicher then stock
6-2.00x7.00 ame o-rings these are 1mm thicker then stock
1-2.00x67.00 ame o-ring this is stock size

I guess if seals don't do it, I can remove/install the pump a little faster. Thanks!

Make sure you check the thread in the Duramax section and Cummins section on the DIY mod for the CP3. If this doesnt help then shoot me a PM. I'm personal friends with 4 of the industry experts on the CP3 system so I PROMISE you they will give you the answer you need or tell you which way to go. :c:

CP3 leaking
 

I have a damp CP3 on top of pump between pulley and where lines come into pump. Oil level is good [not increasing], so can this be the winter wonder you are describing? It is damp, not wet, no drips. 150K miles.