12mm CP3 Tuning....need some help with FCA

Hi all,

New to the forum and need some help tuning this Exergy 12mm CP3. Truck currently won't even drive...

Datalog file and picture are attached of where my issue is happening with truck not moving and engine revved to ~1900rpm (just rebuilt the engine and put the larger pump on in the process).

The issue is very consistent. For the first 25-30sec actual and desired rail pressure are fine and generally in line, but then there it starts to vary up and down as the actual FCA DC increases, and then around 1min 15sec into the run (again very consistent) the FCA DC maxes out and pump loses rail pressure.

I've tried 28 different tune adjustments mainly in the mA duty cycle table and this is the best I've gotten it so far, but as soon as I try to drive I can't go past 5% throttle or it loses pump pressure and starts smoking. Stock pump on this tune ran perfect so nothing should need to be changed with the timing/rp/duration tables. This is also where I had the FCA base table with the stock pump, but going up or down on that table doesn't do anything for the issue. 18psi consistently measured at the lift pump for low pressure side. I do see where its consistently going into the misfire timing table, but not sure why and also don't see how that is currently impacting the fuel side of things.

Any help or support is much appreciated....

Thanks!

What happens if you try a stock tune?

Stock values it varies much worse and more movement on the actual FC DC. Here is a datalog from that: Attachment 153042

you have a leak on high pressure side...connector tube....injector....relief valve on the rail
And idling at 17mm3 is a bit off if pulse table is set correctly it should idle a 10mm3

No visible leaks at any of the high pressure connectors. I forgot to mention checks I?ve done there - I?ve tried swapping rail pressure sensors, removing the PRV return line (only a small drop of fuel on top of the PRV after doing the same run as the catalog), and retorqued connector tubes to 40 ft lbs with no movement on any of the nuts. The truck ran perfect before the engine rebuild on the fuel side of things and each connector tube went back to the same injector on install. If I can?t figure this tune out by later today, my plan is to swap the stock CP3 back in. If it runs fine, then it eliminates the possibility of leaking connector tubes.

There is a reason why tune ask for more pressure and the pressure keep dropping....if it doest "work" with stock setting there is an issue...put back stock cp3 and try again...post a log too

Swapping the CP3 now and will post an update shortly.

Got stock pump in??

Agreed sounds like a leak on high pressure side. Injector or injectors not seated quite right, rail relief valve, cascade valve. Being a new pump shouldn’t be a bad cascade valve though.

Okay....so some updates. I swapped CP3s and the issue remained EXACTLY the same so that rules out the cascade valve and CP3 from the high pressure system. I reconfirmed once again lift pump pressure during the issue and it stays constant at 18psi the whole time with no variation. Also retested the PRV by drying it out and having someone video during the run. It both stayed dry and also didn't visually have any fluid coming out.

So then I decided to go get new connector tubes before the local shop closed and replaced all of the connector tubes and torqued them to 44 ft lbs. The issue remained exactly the same STILL lol....so I tried one more thing which is take the Fluidampr off and flip the tone ring 180 degrees just to make sure I didn't have that flipped upside down when I did the engine swap (I had two new pins/holes from the full power kit on the old engine so that could've been a possibility in my mind). After doing that, the truck won't start at all so I eliminated that possibility and will flip it back in the morning.

I have a hard time believing an injector would just start leaking so much that it can't hold rail pressure when it ran perfect on the fuel side before the rebuild. The injectors were only out of the truck for around a week during that process and both placed on and covered by lint free rags. I always follow the install specs and torque to spec and have never had an issue before this with not having one seated correctly. Wouldn't the connector tube just not even push and click in if it wasn't seated properly?

Since the issue is so consistent with holding and matching rail pressure for the first 20sec or so and then starting to do small adjustments and then big adjustments to the FCA almost like clockwork, I feel like I have a wiring issue where something is not sending the proper feedback to the ECM and its trying to correct something that doesn't need to be corrected. So tomorrow in addition to flipping the timing ring back 180 degrees, I will be back probing each wire in the circuit to test for continuity while moving the harness around so see if I can find anything.

Any other ideas/thoughts are much appreciated! This image is of the datalog post new connector tube install: Attachment 153082

Did you change something else from before rebuilt? In the tune? Post the tune too

No changes to the tune for the last almost 9 years since HP tuners came out and got it dialed in. Instead of jumping to a wiring signal conclusion I decided to just unplug the FCA and watch rail pressure. It went to max as expected and then dropped, which means it has to be mechanical. Once I get this thing running I do plan to get this thread back on track with dialing in the 12mm pump lol. I got some good information from Exergy on flow values vs. FCA DC and mA in the process of all of this. Here is the datalog of FCA unplugged:Attachment 153100

post log instead of picture of it....

conclusion maybe an injector

Quote:

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Originally Posted by xDiesel03

No changes to the tune for the last almost 9 years since HP tuners came out and got it dialed in. Instead of jumping to a wiring signal conclusion I decided to just unplug the FCA and watch rail pressure. It went to max as expected and then dropped, which means it has to be mechanical. Once I get this thing running I do plan to get this thread back on track with dialing in the 12mm pump lol. I got some good information from Exergy on flow values vs. FCA DC and mA in the process of all of this. Here is the datalog of FCA unplugged:Attachment 153100

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Means you got a high pressure fuel side leak, should maintain rail pressure being pegged if there isn’t a leak on the high pressure side.

Well I think I found my issue?I?ve never had this happen before but looks like I had two injectors that didn?t seat all the way.

When I replaced the connector tubes I inspected the old ones for any rings or wear marks to indicate an injector not fully seated, but saw nothing at all. Previously I had the old Bosch style tubes and the new tubes from Cummins are a bright/stainless appearance and also apparently a softer material because when I removed those I found gouges on both the number 3 and 4 cylinder tube.

I wish I had seen that before pulling all six of the injectors lol, but at least I know now. Going to inspect and see if there is a washer stuck in the bore or just wasn?t seated from being a new head. It?s a DJ stage 1 head but not sure if it was bought new or a reman so either thing could be a possibility. Out of 5-6 times I?ve had injectors out and in I?ve never had this happen.

Glad you may have found your issue...it was clearly an high pressure leak issue

Got your leak fixed??

So???

I hope this helps you, but there's a pretty easy outlier here that got missed.

Just tuned a 2003-2004.5 truck the other day and it did something VERY similar to this, and here was the simple fix.

On this particular ECU, you'll want to start with the Transient Main SOI near stock, as with it advanced matching your Steady State Main SOI table, it will result in "MISFIRE" which is what your screenshotted log shows.

Your adjustments will mainly be on Steady State Main SOI only for timing changes.

You'll want to plot your FCA Demanded vs. FCA Actual and then adjust the Duty Cycle (3D Table) OR Current Table (Scalar) to bring the differences within 200psi, which is what I would say is the tolerance.

Focus on response first and the 1000 RPM, 10mm^3 region needs a heavy bump as you are lagging pretty bad initially.

So there you have it, two main fixes to get this thing rollin'. Reach out directly if you need anything else.

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