At this point the only unknowns to the crew (like me) who follows this issue with every development is:
1) Changes of the symmetrical cam CP4. As in, we know the cam lobe was altered for a less aggressive ramp rate. However, I haven't seen or heard of anyone opening up one yet to see if anything else has been changed (such as a keyed lifter).
2) The 2021 pump. There are some rando posts on various forums with people who claim to know "insiders" that bet their farm on the switch back to CP3 (that's why the rumor). Until we see a pump on an actual MY 2021, nobody will know.
3) The parts shortage on the CP4 could be causing FCA to drag their feet on a TSB or recall for the older units. Some theories are they don't want to admit fault, but the pump IS under STAR restriction (internal outfit that deals with repair authorization). FCA could full well end up recalling the older units, but they just got a 3-peat truck of the year and are dealing with worldwide Rona manufacturing shortages. Any new design pumps are going to be reserved for the damaged trucks authorized for repair, and the new trucks coming out of the factory to maintain the sales momentum.
Since I'm here listing stuff might as well go over what we DO know for the new crowd:
1) The CP4.2 injection pump was installed in all 2019-2020 RAM 6.7s. The original had an asymmetrical cam design for the lifter. The theory of failure is that the aggressive ramp rate of the cam lobe contributes to the lifter turning in the bore, effectively kicking the roller off it's intended path, causing it to grind and send metal shavings through the system. Additive companies claim to aid the prevention of this by increasing the lubricity in the fuel, making it "slippery" so the lifter roller doesn't stick and kick to the side. Around early September, a revision to the pump was released
[Pump Identification Link]. It is identified by the large machined dimple in the top right corner. All other small dimples on any of the pumps are nothing but date/mfg coding and do not indicate design differences. The revised pump has a symmetrical cam lobe theorized to lessen the ramp rate of the lifter, reducing the chance of the lifter spinning in the bore.
2) The only reason we know about this pump change is a TSB (technical service bulletin) released by FCA telling the field techs that a specific tune flash needs to be associated with each pump revision. The asym flash will cause NVH (noise, vibration, harshness) on sym pumps and vise versa. This does NOT mean that the pump was revised because of an existing NVH issue. No official word from FCA or Bosch or Cummins has been released on why the pump was revised.
3) Old style asym pumps have been known (from first hand experience testimonials on the net) to grenade between both 2019s and 2020s and at all mileage from just a couple hundred up to 30,000+.
4) There is no known failure rate outside of FCA. The "7%" claim comes from an additive manufacture and has been spread around by other companies. This rate likely includes all CP4s, maybe even including the CP4.1 and CP4.2s on other vehicles like VWs, EcoDiesel, PowerStroke...etc. The failure rate on specifically the 2019+ RAM HD is unusually high for anyone that has followed automotive things on the net for 20+ years. This IS a problem and the hush-hush pump revision is more fuel to that fire.
5) As of this post there is no known failure of the new style sym pump
6) Of all the research I do on this issue on every forum and a few Facebook groups, there has only been one first hand report of a warranty denial due to contaminated fuel on a RAM HD. At first the person was denied for having an aftermarket fuel filter, but after he cited Magnusson-Moss act, the dealer changed their story to contaminated fuel.
7) It is not known how the fuel testing is done. This is in reference to additives. Nobody knows if they are just checking for water, or if they send the fuel through a likely much more complex and technical testing procedure to check for the chemicals that would contribute to added cetane/lubricity/injector cleaning, basically all the stuff that the additives claim to add. Since different fuel companies use different additive packages, I'm not sure how they would be able to find a "base" fuel to standardize from anyway, but there's probably a way.
8) 2021 RAM HD High Output sales literature explains "more fuel flow" contributing to the power rating increase. Does this hint at another pump revision or a different unit? Simply more pressure like the Fords run (that have less failures)? We will see.
I would caution people to disregard any information about the CP4 on other vehicle platforms. Ford still uses it, but they just don't have the failure rates that the RAM HDs saw from 19-20. The pumps are all similar in this CP4 family, but they are specific to the engine design and are specifically "tuned" for certain pressures. There's just something about the ones on RAM HDs that are causing this unusual failure rate.
Also, it would be nice to have a MAIN CP4 thread that we can stick to. There's like 4 different threads going and having all the info in one place would be nice and likely cut down on the perceived fervor over this issue.
