Was contemplating a 2025 6.7 Cummins... Nope!

[jharp]

I spent the last year waiting with bated breath to see what upgrades the 2025 Ram/Cummins combo would have. I, like others, was excited to see the 8 speed transmission upgrade. Like Ford/GM, the 'guts' of the new 8 speed are most likely similar between the entire platform - GM/Ford has the ten speed, which has the same general architecture regardless of vehicle (a Tahoe has the same valve body as a Duramax 3500, as one example.) The ZF 8 speed is really a good transmission... So I have hope there. The 2025 Cummins power bump is also fantastic.

The primary issue I was looking to Ram/Cummins to resolve once and for all was the continual slow motion train wreck that is the high pressure fuel systems on these trucks. Bosch actually makes some interesting high pressure pumps, I've seen with my own eyes the CP9 on large stationary Onan generators. They very rarely fail, they are internally lubricated with engine oil, like the old school P pump engines. Most of the time the high pressure discharge line breaks from vibration and fills the gen enclosure with perfectly atomized fuel mist... But the pump is solid.

From looking at the pictures, the Bosch "CP8" is our old friend with a new name - the CP4, which has come back to haunt us yet again. I'll give it to the sales folks over at Bosch, they really know how to close a deal! Nevermind the fact that Stellantis probably paid out millions to recall all the CP4 trucks from 2019-2022. Perhaps Bosch reimbursed them. Doesn't matter, because judging by the pictures, the "CP8" very much looks like a CP4.

I'll admit I have no idea if the internals look the same. I'm an armchair engineer here... Perhaps they finally pinned the followers so they don't rotate. GM paid out lots over the CP4 issue in the LML duramax trucks - and learned their lesson, they went with Denso as the supplier on the L5P (and the LM2 3.0 duramax) Ford has done an incredible job of landing every failure on the owner's lap over "lack of maintenance" or "buying junk fuel"

I won't be buying one. I hope for the collective sake of all the good people on this forum, and the rest of the folks out there in the world dropping hard earned cash on these $100k mortgage payments on wheels that the new and improved fuel system, really is new and improved.

Those Who Do Not Learn From The Past Are Damned To Repeat It.

 

[flan]

Early on after the recall I wondered if the lower psi of the cp3 caused the truck to run dirty hence the regen issues. We shall see how the 25s do in that regard. Gonna be a wait and see attitude on my end, I imagine they HAD to do something about the rollers in the new model, no company could be that dumb….

 

[AH64ID]

Early on after the recall I wondered if the lower psi of the cp3 caused the truck to run dirty hence the regen issues. We shall see how the 25s do in that regard. Gonna be a wait and see attitude on my end, I imagine they HAD to do something about the rollers in the new model, no company could be that dumb….

Does the CP3 tune run lower pressure?

 

[jharp]

From what I have seen, the limit is more on the high side of the range of the pump, in terms of output pressure.
Under normal/part load conditions, the CP3 and CP4 deliver roughly the same pressure. The CP3 may have to modulate the pressure control valve more to achieve the same pressure, but that would occur normally as part of the control loop between the rail pressure sensor and the pump pressure control.

There is some upper level engine load value where the CP3 runs out of capacity, hence the lower upper limit of pressure. I've wondered if a straight CP3 swap into a CP4 truck would generate 'low rail pressure' codes at WOT....

 

[AH64ID]

From what I have seen, the limit is more on the high side of the range of the pump, in terms of output pressure.
Under normal/part load conditions, the CP3 and CP4 deliver roughly the same pressure. The CP3 may have to modulate the pressure control valve more to achieve the same pressure, but that would occur normally as part of the control loop between the rail pressure sensor and the pump pressure control.

There is some upper level engine load value where the CP3 runs out of capacity, hence the lower upper limit of pressure. I've wondered if a straight CP3 swap into a CP4 truck would generate 'low rail pressure' codes at WOT....

I'll need to look at the ECM files for a 21, but I have not noticed my truck making any less peak rail pressure than the advertised pressure for a CP4 CGI truck.

 

[Brutal_HO]

From what I have seen, the limit is more on the high side of the range of the pump, in terms of output pressure.
Under normal/part load conditions, the CP3 and CP4 deliver roughly the same pressure. The CP3 may have to modulate the pressure control valve more to achieve the same pressure, but that would occur normally as part of the control loop between the rail pressure sensor and the pump pressure control.

There is some upper level engine load value where the CP3 runs out of capacity, hence the lower upper limit of pressure. I've wondered if a straight CP3 swap into a CP4 truck would generate 'low rail pressure' codes at WOT....

I've never heard of any of the owners that did the pre-recall CP3 swaps having any issues and most did not have tunes, just a straight up swap.

 

[Jawillmo]

Does anyone know if Ram/Cummings redesigned the grid heater? I have had one engine failure, and two separate P2609 faults (grid heated) . Engine failat 37k, grid failure at 40k and again at 50k.

 

[Xflight29]

I spent the last year waiting with bated breath to see what upgrades the 2025 Ram/Cummins combo would have. I, like others, was excited to see the 8 speed transmission upgrade. Like Ford/GM, the 'guts' of the new 8 speed are most likely similar between the entire platform - GM/Ford has the ten speed, which has the same general architecture regardless of vehicle (a Tahoe has the same valve body as a Duramax 3500, as one example.) The ZF 8 speed is really a good transmission... So I have hope there. The 2025 Cummins power bump is also fantastic.

The primary issue I was looking to Ram/Cummins to resolve once and for all was the continual slow motion train wreck that is the high pressure fuel systems on these trucks. Bosch actually makes some interesting high pressure pumps, I've seen with my own eyes the CP9 on large stationary Onan generators. They very rarely fail, they are internally lubricated with engine oil, like the old school P pump engines. Most of the time the high pressure discharge line breaks from vibration and fills the gen enclosure with perfectly atomized fuel mist... But the pump is solid.

From looking at the pictures, the Bosch "CP8" is our old friend with a new name - the CP4, which has come back to haunt us yet again. I'll give it to the sales folks over at Bosch, they really know how to close a deal! Nevermind the fact that Stellantis probably paid out millions to recall all the CP4 trucks from 2019-2022. Perhaps Bosch reimbursed them. Doesn't matter, because judging by the pictures, the "CP8" very much looks like a CP4.

I'll admit I have no idea if the internals look the same. I'm an armchair engineer here... Perhaps they finally pinned the followers so they don't rotate. GM paid out lots over the CP4 issue in the LML duramax trucks - and learned their lesson, they went with Denso as the supplier on the L5P (and the LM2 3.0 duramax) Ford has done an incredible job of landing every failure on the owner's lap over "lack of maintenance" or "buying junk fuel"

I won't be buying one. I hope for the collective sake of all the good people on this forum, and the rest of the folks out there in the world dropping hard earned cash on these $100k mortgage payments on wheels that the new and improved fuel system, really is new and improved.

Those Who Do Not Learn From The Past Are Damned To Repeat It.

I cannot imagine Ram, like you said after spending millions of $$$ and the nightmare of the CP4 make another bad choice in their fuel pump.

 

[F3arl3sslimited]

Does anyone know if Ram/Cummings redesigned the grid heater? I have had one engine failure, and two separate P2609 faults (grid heated) . Engine failat 37k, grid failure at 40k and again at 50k.

The 25 has glow plugs now, not a grid heater

 

[4Dodges]

Saw a video a while back where ram was pointing out all the improvements to the new 6.7 engine. He stated their engineers performed ( a kill the pump tests) the newer CP4 passed it fine but said their new CP8 totally crushed it. Made me feel like they did address the past pump issue. This along with the new tranny heavy duty pistons and easier service ability is why I pulled the trigger on a 4500... fingers crossed

 

[AH64ID]

From what I have seen, the limit is more on the high side of the range of the pump, in terms of output pressure.
Under normal/part load conditions, the CP3 and CP4 deliver roughly the same pressure. The CP3 may have to modulate the pressure control valve more to achieve the same pressure, but that would occur normally as part of the control loop between the rail pressure sensor and the pump pressure control.

There is some upper level engine load value where the CP3 runs out of capacity, hence the lower upper limit of pressure. I've wondered if a straight CP3 swap into a CP4 truck would generate 'low rail pressure' codes at WOT....

There are no peak pressure differences in an OEM tune for a CGI CP4 vs a CGI CP3. Over 99% of the rail pressure map cells are identical and the very very few that are different have the CP3 truck making slightly more pressure. They both command as high as 2000 bar (29007 psi).

The CP3 is used in a lot higher hp motors than these trucks and doesn't run out of fuel capacity that easily. It's a very capable pump that has no issues in the CGI 6.7 making 29K psi.

If a CP3 truck gets a low psi code then something is wrong.

 

[H3LZSN1P3R]

There are no peak pressure differences in an OEM tune for a CGI CP4 vs a CGI CP3. Over 99% of the rail pressure map cells are identical and the very very few that are different have the CP3 truck making slightly more pressure. They both command as high as 2000 bar (29007 psi).

The CP3 is used in a lot higher hp motors than these trucks and doesn't run out of fuel capacity that easily. It's a very capable pump that has no issues in the CGI 6.7 making 29K psi.

If a CP3 truck gets a low psi code then something is wrong.

I think the biggest running difference between the CP3 and the CP4 was how fast it could build pressure

 

[AH64ID]

I think the biggest running difference between the CP3 and the CP4 was how fast it could build pressure

Since the demanded charts are the same if the CP3 couldn’t keep up it would trip a CEL, so they must be pretty close.

There might be subtle differences, but I don’t think they are appreciable under most circumstances.

 

[H3LZSN1P3R]

Since the demanded charts are the same if the CP3 couldn’t keep up it would trip a CEL, so they must be pretty close.

There might be subtle differences, but I don’t think they are appreciable under most circumstances.

I agree the CP4 is capable of higher pressures than a CP3 but Ram did not utilize that aspect of the pump it was likely the “cheaper” option at the time even though they kept the tuning within the CP3 range. With the minimal other difference with the pumps I can only assume it was the price difference only which caught up to them in the end anyway.

 

[flan]

Early on it was questionable if there were pressure differences, because there were 2 distinct reflashes available if you had a CP3 truck or CP4 truck. If the tech did the wrong tune the truck wouldn’t run correctly.

 

[johnmyster]

If the HPFP is your hill to die on, then I guess you're a GM buyer and you can rationalize valve body replacement. Nothing to be ashamed of. They're great trucks.

Or you can be a ford buyer and rationalize DCR conversion.

Unlike the Ford, the cummins HPFP is mounted on the side of the engine. Easy access, and space enough to have options. If the 2025+ trucks begin to grenade pumps, I'm sure the aftermarket will quickly respond with a solution. If this is the only weakness of the truck, it's a solvable one. We also know from the Ford 6.7 vs GM LML situation, the CP4 survivability tended to be better with good filtration and lift pumps. Both of those are present, so just like on the Fords, it should buy some time before the odds of failure are significant.

The trick is not to run faster than the bear. Run faster than your friend. If you're a low mileage driver you'll still be covered under warranty when the hot shot community reports failures.

In my opinion, other weaknesses have been addressed. CGI, transmission, and grid heater. Supposedly the CGI swap will mitigate cam/lifter root causes. I'd look hard if I had the need and wanted to have more funds allocated to a depreciating toy.

 

[jharp]

It's strange to me that these are the solutions the aftermarket has to come up with. To your point johnmyster, you can buy aftermarket valve bodies for the GM 10 speed. You can buy disaster prevention kits for if/when the CP4 grenades on the Ford. If the "CP8" pump starts grenading, they will probably come up with a CP3 retrofit kit.

I'm mostly shocked that Bosch is still the fuel system supplier to cummins after all the recalls and problems they've had. I do hope the "CP8" pump at least pinned the followers so they don't rotate.

 

[johnmyster]

It's strange to me that these are the solutions the aftermarket has to come up with. To your point johnmyster, you can buy aftermarket valve bodies for the GM 10 speed. You can buy disaster prevention kits for if/when the CP4 grenades on the Ford. If the "CP8" pump starts grenading, they will probably come up with a CP3 retrofit kit.

I'm mostly shocked that Bosch is still the fuel system supplier to cummins after all the recalls and problems they've had. I do hope the "CP8" pump at least pinned the followers so they don't rotate.

I'll get flamed, but...

Because by the time the failures have become widespread, the R&D folks at the OEM are focused one or two platform revisions into the future. There is very little R&D durability testing time available before product release. As long as the majority of vehicles make it past warranty, the OEM really can't/doesn't care. Their lawyers tell them it's cheaper to deny and cover up than to redesign and address. For the aftermarket, the overall small percentage of failures plus those owners that they can scare into preventative measures is worth it. For the OEM, not so much.

I worked in the fuel injector factory for the 6.0 Powerstroke, circa 2002-2004. I'm amazed that platform ever survived in the wild based on some of the challenges we were addressing at crunch time.

If we refused to buy anything but perfect trucks we wouldn't have trucks.

 

[gimmie11s]

I spent the last year waiting with bated breath to see what upgrades the 2025 Ram/Cummins combo would have. I, like others, was excited to see the 8 speed transmission upgrade. Like Ford/GM, the 'guts' of the new 8 speed are most likely similar between the entire platform - GM/Ford has the ten speed, which has the same general architecture regardless of vehicle (a Tahoe has the same valve body as a Duramax 3500, as one example.) The ZF 8 speed is really a good transmission... So I have hope there. The 2025 Cummins power bump is also fantastic.

The primary issue I was looking to Ram/Cummins to resolve once and for all was the continual slow motion train wreck that is the high pressure fuel systems on these trucks. Bosch actually makes some interesting high pressure pumps, I've seen with my own eyes the CP9 on large stationary Onan generators. They very rarely fail, they are internally lubricated with engine oil, like the old school P pump engines. Most of the time the high pressure discharge line breaks from vibration and fills the gen enclosure with perfectly atomized fuel mist... But the pump is solid.

From looking at the pictures, the Bosch "CP8" is our old friend with a new name - the CP4, which has come back to haunt us yet again. I'll give it to the sales folks over at Bosch, they really know how to close a deal! Nevermind the fact that Stellantis probably paid out millions to recall all the CP4 trucks from 2019-2022. Perhaps Bosch reimbursed them. Doesn't matter, because judging by the pictures, the "CP8" very much looks like a CP4.

I'll admit I have no idea if the internals look the same. I'm an armchair engineer here... Perhaps they finally pinned the followers so they don't rotate. GM paid out lots over the CP4 issue in the LML duramax trucks - and learned their lesson, they went with Denso as the supplier on the L5P (and the LM2 3.0 duramax) Ford has done an incredible job of landing every failure on the owner's lap over "lack of maintenance" or "buying junk fuel"

I won't be buying one. I hope for the collective sake of all the good people on this forum, and the rest of the folks out there in the world dropping hard earned cash on these $100k mortgage payments on wheels that the new and improved fuel system, really is new and improved.

Those Who Do Not Learn From The Past Are Damned To Repeat It.

Im no CP4 fan, but at least on the Ford's supposedly the pistons or followers are now pinned and cannot rotate in their bores. I believe that started in 2022 for Ford.

Here's to hoping Ram is doing the same thing with this pump.

 

[H3LZSN1P3R]

I'm mostly shocked that Bosch is still the fuel system supplier to cummins after all the recalls and problems they've had. I do hope the "CP8" pump at least pinned the followers so they don't rotate.

Bosch is not the issue. Cheap people at FCA buying the low end parts is they are trying to build cheap sell high, typical corporate greed.