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Thread: CP3 - Engine Knock

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    Davey's Avatar

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    CP3 - Engine Knock

    Hello all, I’ve got 2015 6.7 with 80k miles.

    I’ve always had this engine knock but never an issue with fuel mileage or the truck's overall performance.

    The noise is getting slightly louder, and the research I’ve done shows it to be a CP3 knock.

    Some say they have retimed the CP3 to sync with some cylinders at TDC and have fixed the noise, and the engine is much quieter.

    I cannot find any videos on how to do this, or if anyone has attempted this procedure to please walk me through this.

    From what I understand is I’ll need a steering wheel puller or a harmonic balancer puller.

    The idea is to remove the CP3 gear and rotate the motor 30 to 60 degrees to sync the CP3 equipment.

    If not in sync, the backlash is the result of the knock that I’m hearing.

    I appreciate any help you can provide.


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    Grassroots1964's Avatar

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    Re: CP3 - Engine Knock

    I have a '16 & I believe I have the same issue you are describing. I, too, looked high and low and found the same answers about being out of sync.

    I did take it to a reputable diesel shop, which only works on Cummins, & they said they could sync, but there are zero issues with the noise it is making.

    I still don't feel comfortable with that answer, but I am not an expert either.

    The noise drives me nuts!!

    Every time I start it, I become hyper-focused on the sound!

    I posted this same question last year and didn't receive clarity.

    You can look me up by name and see the posts.

    Mine sounds like a tapping sound....like tink..tink..tink at idle.

    When you increase RPMs, it seems to go away.

    I'll keep monitoring this site, and if you find anything out, please add it.


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  5. Top Of Page | #3
    TheJonJon's Avatar

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    Re: CP3 - Engine Knock

    Change fuel filters, add fuel treatment and see if that helps.

    It's a Cummins, though.

    They make noise.

    Worry if they don't.


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  7. Top Of Page | #4
    Jeeptony's Avatar

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    Re: CP3 - Engine Knock

    I came across this a while back, I hope it helps someone.

    2011 3500 SRW Laramie 4×4, 68RFE with billet valvebody. 6.7HO with S&B intake, 5" exhaust, ARP headstuds, Industrial Injection R1 injectors, Fass 165, RaceMe Ultra tuned by DRD, Bilstein shocks, reverse leveled on 285/65/18 Nitto G2s and Raceline wheels, traction bars, B&W gooseneck hitch, Kicker audio, Morimoto and GTR lighting, Uniden R7.

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