Thanks Thanks:  18
Likes Likes:  17
Results 1 to 5 of 5

Thread: What is a CP3?

  1. Top Of Page | #1
    guru of all things diesel Canadiandiesel's Avatar

    User Info Menu

    What is a CP3?

    The CP3 High-Pressure Common Rail Pump

    This pump features 3 plungers, it is of variable displacement. All CP3's from the light-duty engines, such as 5.9 and 6.7 as well as the Duramax engines, have the same bore and stroke for the plungers. There are none that are any larger unless they are modified to increase the displacement. These pumps only produce about 80% efficiency based upon the available displacement, in stock form. The pump is driven from the cam gear and runs 1:1 with the engine speed in rpm.

    Fuel enters the CP3 and goes directly to the gear pump for pressurization. From there tied into the circuit is a regulator. This regulator limits internal pressure for several purposes, supply to the pumping plungers, lubrication and air removal which returns to the tank and returns for overfill back to the fuel inlet. The priority is for the supply of fuel for the plungers, second is for lubrication, and the third is for over pressurization which bleeds back to the inlet. The gear pump, pressurizes the supply fuel to higher levels for its independent circuits, according to the setpoint of the regulator (cascade valve).

    Internally the pump acts much like an engine, the plungers represent pistons, unlike a piston in an engine, the plungers use clearance to seal the bore, where an engine uses pistons rings. This clearance is not measurable with conventional tools, as most don't have enough zeros behind the decimal point. The plungers are actuated by an eccentric shaft, which operates a cam. The cam converts vertical lift to vertical/horizontal movement that allows the tappet to slide as it raises the plunger. The tappet is used to concentrate the load to the center of the plunger, this negates side loading of the plunger to the bore to increase overall life. The plunger also has a return spring to return its movement for fuel charging. Each plunger is separated by 120 degrees, this translates to the same amount of engine crankshaft rotation for the next pressure delivery to complete.

    Fuel travels through several twists and bends, to arrive at the delivery valve. Once the plunger begins to descend the bore, it begins to fill the chamber with fuel. The amount is dependent upon several things, otherwise, it will not be filled to a suitable level, which will inhibit performance and rail pressure (variable displacement). Once the plunger begins its pressurization stroke, the spring-loaded delivery valve is forced closed and backpressure in the high-pressure side of the pump determines the extent of the pressurization. Once this pressure is exceeded, fuel exits the chamber (bore) and enters the high-pressure side of the pump. This fuel travels past a spring-loaded ball and seat arrangement, that re-seats for the next event. This is the area in which the little ball is so crucial, if it does not reseat due to being absent or if it is delayed due to a weak spring, then the high-pressure fuel flows back and cannot be pressurized to the higher level. This is where catastrophic failure takes place. Usually, the plunger is compressed to the point that it shatters and blows the access plugs from the side of the pump.

    MPROP, measuring unit, fuel control actuator, solenoid, fuel pressure regulator
    It is termed by many different names, but its duty is to supply fuel to be pressurized, it is not extremely efficiency by design and has all the control over fuel delivery. As with many circuits and components inside the pump, there is room for improvement. Some of the things add to greater volumetric efficiency, which means to get as close in delivery as the pump can displace in volume. Other things are to add to the displacement by several means. This makes the pump bigger, just like a 6.7 is larger in displacement than a 5.9 (bore and stroke).

    In recent testing a supply pressure of 20 psi seems to be ideal for the CP3, life will also be extended with good filtration and water-free fuel. Some of these pumps look as good as new with 100,000 miles on them some are worn out with less than 10,000 on them. I guess it just depends upon how good the fuel is.

    1. The stock lift pump is supposed to push out at MIN 11.5 PSI. All the books say for the GPH is that the flow is sufficient to supply the injector pump. It draws 5 amps at the max flow and is 100% duty cycle.

    2. Fuel heater if not working properly can cause a wax build-up (unlikely unless in very extreme cold weather ie -30 cels or below), or may cause blue and or white smoke. If the fuel is below 45 F +/- 8 F the fuel heater will turn on and then turn off once the fuel temp in the element reaches 75 F +/- 8 F. Cold Fuel will cause white smoke. Interesting. I truly wonder what the re-flashes are from DC to fix these symptoms. Are all they doing is changing the heater's parameters to preheat the fuel?

    3. FCA fuel control actuator. Its job is to control the amount of fuel entering the low-pressure side of your injector pump. It is a solenoid-operated valve located on the bottom driver side of your pump. The ECM controls the action of this valve. Fully open and it has a full flow of fuel into the High-pressure side of the pump. closed and it will shut off the fuel supply... Why is this important? After talking to a few mechanics about some issues one thing that was brought up about the FCA and it having premature wear on it. This causing it to not work properly. If the ECM is demanding that fuel be stopped and it is getting by the FCA then this is causing to much fuel to enter the high-pressure chambers, this, in turn, will cause to much fuel to be routed to your injector rail. At the end of the day, how does this affect a person? To high of pressure and the end result is leaking injectors. because the fuel pressure is too great within the rail system.

    4. The overflow valve is another problem area that seems to be causing a few problems within some of the newer trucks. If this valve gets dirty and cannot open then fuel pressure cannot bleed off and you will get a pressure spike. Although this is unlikely.
    If the opposite happens and the valve will not close properly then you will have a loss of pressure within the Injector rail system. this, in turn, will result in poor fuel economy, loss of power and also an incomplete burn as the injectors will not be able to give the proper amount of fuel into the chamber.

    5. Next is the Fuel Pressure sensor. It controls when the overflow valve will open and close. both the sensor and the overflow valve are mounted on the fuel rail. If this sensor fails then your truck will go into limp mode or wont run at all. The sensors are pretty reliable but they are the key to the whole system.

    6. The fuel filter. filters down to 10 mics but it been proven by bosch this fuel system requires 3 mics of filtration to work properly A few of the dealerships have stated that injector wear is being caused by poor fuel filtration.



    Vital components on the CP3
    1. Flange
    2. Shaft
    3. Polygonal ring
    4. Housing
    5. Gear pump
    6. Overflow valve
    7. Low-pressure inlet
    8. Metering unit
    9. Back flow connector
    10. High-pressure connector
    11. Plunger
    12. Bucket
    13. Suction valve
    14. High-pressure valve (out to rail)


    Last edited by Canadiandiesel; 05-09-2013 at 11:46 PM. Reason: added pump

  2. Top Of Page | #2
    CMB's Avatar

    User Info Menu

    Re: What is a CP3?

    Thanks for taking the time!

    2012 Ram 3500 Laramie, 3" BDS Coil over, DuraFlap, 68RFE, 4.10, 35s, Front receiver, Krown protected

  3. Thanks IGOTACUMMINS, cumminsbadgirl thanked for this post
    Likes IGOTACUMMINS, cumminsbadgirl liked this post
  4. Top Of Page | #3
    WE WILL STAND! IGOTACUMMINS's Avatar

    User Info Menu

    Re: What is a CP3?

    We forget about this thread!

    Glad to see it back again!!

    "The grass is greener where you water it"


  5. Likes cumminsbadgirl liked this post
  6. Top Of Page | #4
    Murph's Avatar

    User Info Menu

    Re: What is a CP3?

    Wow awesome breakdown!

    That being explained, brings me to two questions.

    1 best dual fuel filters or best singular filter recommendations?

    2 should we be using an additive to help with the lubrocity loss by lower sulfur in diesel fuels.

    Since this my first diesel forgive me if this seems retoricle as I’m sure these questions have by seen by some of the senior members here.

    I just remember some cross tale that with the lower sulfur count we were losing some lubrocity for the injectors hence a shortened life span or is this more common with duramax and p/s?

    Thx for the time and share.


  7. Thanks cumminsbadgirl, SSOutlaw thanked for this post
    Likes cumminsbadgirl liked this post
  8. Top Of Page | #5
    #1 VENDOR cumminsdieselfreak's Avatar

    User Info Menu

    Re: What is a CP3?

    Quote Originally Posted by Murph View Post
    Wow awesome breakdown!

    That being explained, brings me to two questions.

    1 best dual fuel filters or best singular filter recommendations?

    2 should we be using an additive to help with the lubrocity loss by lower sulfur in diesel fuels.

    Since this my first diesel forgive me if this seems retoricle as I’m sure these questions have by seen by some of the senior members here.

    I just remember some cross tale that with the lower sulfur count we were losing some lubrocity for the injectors hence a shortened life span or is this more common with duramax and p/s?

    Thx for the time and share.
    1. A FASS fuel/filtration system would be very beneficial for your 2010 as you don't have the dual filters that the 13+ trucks have.

    2. This is a very debated topic. ULSD (ultra low sulfur diesel) is very dry.

    I use fuel additives to restore lubricity as it helps me sleep better at night knowing I'm doing everything I can to help my truck.

    Fuel filtration is key to longer lasting injector life but is often overlooked by some owners.

    2018 Ram 2500 4x4 G56
    Romans 10:13

    See what we are up to on:
    FACEBOOK | INSTAGRAM
    Or Email me at:
    joe@ddpmotorsports.com
    www.ddpmotorsports.com


  9. Thanks Murph, SSOutlaw thanked for this post
    Likes cumminsbadgirl, AK Bob, Murph liked this post

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •