QSC 8.3 CM554 - No Start hard to diagnostic

[J99]

Hello,

Still facing a no start condition (only few seconds then dies) on a QSC 8.3 CAPS CM554. Fault Code down to error 276 (High current detected on injection control valve stator return) and sometimes error 456. Pressures look all good during cranking (5000 to 6000 PSI in accumulator). Quite some things already done:
- New Fuel Filters (both inline one + water separator one)
- Cleaned Lift Pump, pressure in spec
- New CAPS Fuel Pressure Sensor
- New Transient Suppressor
- New Injection Control Valve Stator + ICV Repair Kit done
- Updated ECM to latest official Cummins calibration for the model (J91384.12)
- All Click Tests work fine (on ICV and on pumping valves)
- Removed air up to injectors lines plugs into cylinder head

And still error 276...doing the procedure again, it comes down to asking to replace again the transient suppressor (step 3C-1 added late in the procedure) even when test is OK, or later on, to replace the Injection Control Valve.

I strongly suspect no mechanical issue as when starting a few seconds, it seems to run well, and it was working the day before we stopped it...

I would like to bypass error 276 to check at least if it is electronic only or mechanical, but I don't find the CAGT Block Fault Code Parameter in Calterm for these old ECM. I don't know what else to think of here...

Any idea how to block codes on these ECM ? or better diagnostic ideas / what to try next ?

Thanks for your help

[J99]

After another start attempt with the Transient Suppressor unplugged, it finally fired up for good ! Error 539 (open circuit on transient suppressor, possible ECM damage...), but expected.

After 2 good restarts without it, plugged it again, and it also worked fine ! No more error 276 or others.

So I guess my last main change with the Stator of the Injection Control Valve was the good one...hopefully ! Until next chapter of the long story of CAPS pumps issues...

[J99]

Next chapter was next morning...it did not want to start again (only few seconds then dies) despite working the day before...code 456 at each attempt, and 276 too at some.

As I saw on Calterm that the fuel pressure at start of injection command was low (820 psi, compared to 4000 - 5000 the day before), I suspected some obstruction in the accumulator (before the fuel sensor which is the one shooting error 456). So I went ahead and opened the CAPS accumulator to check it and clean it.
Nothing special found in it except some dirt from old fuel but I cleaned all with ultrasonic + revived the key valves and contact surfaces, and reassembled it.

And it fired again this time, no error code, looks to work normal after a few stop and restarts ...let's see for how long. I hope this could help others.