Ok, the semi i drive at work is having issues no one (not even a dealer) can figure out...

Its got a M11 Cummins

It will run like hell for bout 15 minutes, then slowly begin to lose RPMs at wide open throttle, untill finally it wont tach over 1100 then it stalls.

New injectors, TPS and ECM, same problem.

But heres the kicker, you shut the key off, start it back up, itll be fine again for a bit...

Input?

Sounds like a sensor on the warm run circuit is bad trimming the fuel til it stalls out.

What exactly does the warm run circuit have in it?

Should be a switch under the dash by the plug in( obd2 style but cummins inline) flip it to eng diag position, turn key on and see what codes its throwin...
its goin into limp home mode and is derating itself severly( motor thinks its blown up) fuel filters, check all sensors, unplug and see if oils leakin into any of them especially cam crank and oil pressure sendin unit....only been around 2 m11s but they were usually pretty easy to figure out....

Also does it/ will it blow any smoke before it starts actin up? Could be fuel lines suckin themselves shut, or even the tanks not venting properly...try poppin the cap(s) when it starts actin up and see if that changes anything....

Ive experianced both and nobody between salt lake city and home could figure it out...get home and my uncle found my fuel lines were suckin shut from tanks not venting, new caps and fuel line and no more problems( my old fld n14)

The warm or run circuit is when it takes input from the sensors and not the computer defaults it runs at startup.
Flow Red's advice Cummins has a reader that will show ask the sensor voltages/resistance. This will help to compare to the normal range limits per Cummins manual.

Had a bus that died at random times then started right up.
It was a foil seal off a fuel conditioner bottle in the tank that sucked onto the pickup tube shutting the fuel flow off. Engine died suction stopped and foil floated away and it would start.
This one sounds like a sensor issue.

Www.dieselserviceparts.com has a run down of every fault code known to Cummins...very helpful info when on the side of the road.... key on engine off with the switch flipped the stop engine light will flash a 3 number code, if its derating compleatly to stall out, theres gotta be a code and my guess would be fuel or oil pressure related as those are the only ones that will shut it down unless its over heated to 250*+....

smokey said:

Had a bus that died at random times then started right up.
It was a foil seal off a fuel conditioner bottle in the tank that sucked onto the pickup tube shutting the fuel flow off. Engine died suction stopped and foil floated away and it would start.
This one sounds like a sensor issue.

Click to expand...

Done that too...pita to get out....2" long x line size screens on all pickup tubes kept that from happenin again......

Well, i passed along all your suggestions, 3 shops and 6 months later the problem was a damn injector pump.

Workin' Rig said:

Well, i passed along all your suggestions, 3 shops and 6 months later the problem was a damn injector pump.

Click to expand...

Usually injector pumps arnt intermitant.....

Thats what i thought...

Im no diesel mechanic, but they said something about a splined shaft on the bottom of the pump that the splines were stripped off?? Allowing it to catch sometimes, othertimes not??

Workin' Rig said:

Thats what i thought...

Im no diesel mechanic, but they said something about a splined shaft on the bottom of the pump that the splines were stripped off?? Allowing it to catch sometimes, othertimes not??

Click to expand...

More like broke at an angle......i have seen pumps give out because of fuel restriction...if it acts up again id do new fuel lines....might do em anyway...

My '97 5.9 acted in similar fashion (no power pulling a heavy trailer) back in October - mechanical injector pump is wearing out. Cranked the adjustments out to the max and I'm back in business, but my mechanic said to start saving $$ for a new one as it's just a matter of time.

mtflat said:

My '97 5.9 acted in similar fashion (no power pulling a heavy trailer) back in October - mechanical injector pump is wearing out. Cranked the adjustments out to the max and I'm back in business, but my mechanic said to start saving $$ for a new one as it's just a matter of time.

Click to expand...

97 is p pumped, stockers are found pretty easy, many aftermarket options too....i would suggest aftermarket, stockers wernt built with dry ulsd in mind.....