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.

 

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!

 

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?

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. If you really want to help read on and I will explain why your theory has so many holes in it.

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.