2012 ISX 12 CM2250 - rough under throttle

[Alan50gt]

(03-31-2022 )tree98 Wrote:  So when the rail pressure was at 29k did you shut the engine down and see how fast it would leak off? What you want is less than a 4000 psi drop in 1 minute.
If it falls off quicker than that, you start capping injectors and running the test again. If the leakdown rate improves, you know the injector you capped off is bad.
Maybe you have an injector or 2 hanging open? You say they were replaced 200k ago, do you know if they were replaced with factory cummins or some ebay junk?
Is the engine making oil?

I forgot to mention, you need to open a separate data monitor window in insite to watch the rail pressure.

HP fuel testing was completed with the truck up to temp. Once the FPRV was replaced she holds well. 30k for quite a long time (10 min range) or until restart. They are genuine Cummins RX/PX reman injectors. THEY ARE AT AN INJECTOR SHOP AS WE SPEAK. So far there is a delivery issue at some specific period with 1 of them (some tech talk I dont understand, and I didnt speak to them directly), other 5 checked out. Were going to get that one new, and theyll run a baseline against the other 5.

I had capped injectors individually and in pairs when cold, No improvement in running condition. Did not repeat leak back testing when cold because it will not run well enough. Original leak back for all injectors was well below threshold @1 oz total across all 6 (4 oz allowed)

Not convinced the single injector is the issue but we'll see