[MiBowhunter]

hello, i’m new here to the forum and also to the Cummins. Been a powerstroke guy for 20 yrs, familiar with diesels but learning more on the Cummins . i have a 2017 Ram 3500 6.7 Cummins with an issue. I had a code for the turbo actuator and was in fact a bad actuator, turbo sector shaft etc was checked as well and calibrated (trip #1 to the dealership). two weeks later truck would lose throttle for about 5 secs, eventually stall and hard crank to start, no codes.. then run fine and do it again. took it back to the dealer the said the re-flashed the ECM. two weeks later did the same EXACT thing. Have 2 friends who work for Cummins (not Ram) and on the 6.7. When i explained the symptoms, they said EGR valve gets stuck open, excess exhaust fills the cylinder and smothers the engine. hard crank is trying to rid itself of tge exhaust. explained this to the dealer. they kept it for 2 weeks and said they got it to stall and put a new EGR valve on (trip #3 to dealership). Ran hard and really well for about weeks and again…. exact same thing. Cummins guys said check for short circuit in ECM could be shorting the EGR. back to dealer and explained. they said Ram tech support would not look at it because it has a fass system. (professional installed, new filter and new mopar filters on engine and chassis). truck doesnt buck or anything that would indicate a fuel issue. Now.. truck is stock with 27k miles, Cummins friends work with post-assembly issues on this yr and engine, said that yr truck had ALOT of EGR failures, symptoms match perfect especially with the low miles. I told the dealer to check the ECM connections, harness etc for any shorts and replace the EGR again (plan on deleting it soon). have ANY of you ever ran into this issue? sorry for the long post.. figured you needed the entire story, thx

 

[Southernmusic]

Never heard of an ecm wiring issue for egr. But you could set up a simple monitor

 

[Shock88]

i’ve never heard of that issue…but as the guy above me said, i would try and find out it’s position, possibly keeping it shut manually if ur running out of ideas

 

[MiBowhunter]

i’ve never heard of that issue…but as the guy above me said, i would try and find out it’s position, possibly keeping it shut manually if ur running out of ideas

good idea! they dealership is putting a “black box”(??) type of monitor and driving it to see if they can find the issue when it occurs. what my friend said at Cummins makes sense to me its just puzzling on the “why” the EGR sticks open at random. Does anyone thinkbit’s the FASS system? ive ran them fr yrs with zero issues so again.. i dont think its a fuel issue.

 

[StealthDiesel]

You sound too focused on the EGR valve. You don't have any EGR DTC's and it's been replaced twice.

You don't mention that you are monitoring high side rail and low side lift pump fuel pressures.
I would recommend monitoring both of these. Especially the low side fuel pressure since you have a FASS.
It could very well be a fuel system issue.

I would also recommend to monitor battery voltage with an independent voltmeter in the cab.

Monitoring these parameters would at least eliminate several variables.

 

[Lins]

You sound too focused on the EGR valve. You don't have any EGR DTC's and it's been replaced twice.

You don't mention that you are monitoring high side rail and low side lift pump fuel pressures.
I would recommend monitoring both of these. Especially the low side fuel pressure since you have a FASS.
It could very well be a fuel system issue.

I would also recommend to monitor battery voltage with an independent voltmeter in the cab.

Monitoring these parameters would at least eliminate several variables.

Agreed. I also don't see how excess exhaust in the cylinder would be hard for the engine to crank over as the OP stated.

 

[MiBowhunter]

You sound too focused on the EGR valve. You don't have any EGR DTC's and it's been replaced twice.

You don't mention that you are monitoring high side rail and low side lift pump fuel pressures.
I would recommend monitoring both of these. Especially the low side fuel pressure since you have a FASS.
It could very well be a fuel system issue.

I would also recommend to monitor battery voltage with an independent voltmeter in the cab.

Monitoring these parameters would at least eliminate several variables.

thx that does help alot! that is my next step. ECM checked out good including all connections. EGR was cycled and seem to function ok. so.. going with my friend at Cummins is putting me back to the FASS system may be causing an issue? He stated that truck has a CP3 pump and with stock or even a small tune (for deleting maybe +20hp) he said the factory fuel filters and pump is more than fine.. and that the FASS system could be doing weird stuff.

 

[MiBowhunter]

Agreed. I also don't see how excess exhaust in the cylinder would be hard for the engine to crank over as the OP stated.

lins.. in regards to the excess pressure not causing the hard crank.. can you educate me please?

 

[Lins]

lins.. in regards to the excess pressure not causing the hard crank.. can you educate me please?

Why would there be excess pressure while cranking? It's not even making exhaust yet while cranking, it's still trying to suck air into the engine...

 

[MiBowhunter]

Why would there be excess pressure while cranking? It's not even making exhaust yet while cranking, it's still trying to suck air into the engine...

so the way it was explained to me.. there would be exhaust in the cylinder from the egr stuck open.. an abnormal amount of exhaust.. it’s that exhaust that it is trying to get out from cranking to allow fresh air in to start.

 

[Lins]

so the way it was explained to me.. there would be exhaust in the cylinder from the egr stuck open.. an abnormal amount of exhaust.. it’s that exhaust that it is trying to get out from cranking to allow fresh air in to start.

Even if that was possible, after a revolution or two of cranking with no combustion, there would be no more exhaust as the engine wouldn't have made any...

 

[MiBowhunter]

makes sense.

 

[Builderdude]

One exhaust stroke of the piston would expel the hypothetical “extra exhaust gas”. Also I don’t think the Cummins would have any difficulties compressing said “extra exhaust gasses” that were supposedly still in there.

 

[MiBowhunter]

One exhaust stroke of the piston would expel the hypothetical “extra exhaust gas”. Also I don’t think the Cummins would have any difficulties compressing said “extra exhaust gasses” that were supposedly still in there.

thx, yeah i agree, after further research i think that view doesnt make sense either. i figured out is was a fuel issue (thank you stealthdiesel). seems it was the draw straw from the FASS and how the sending unit was modified which lead to air in the system or not enough fuel in the basket.. 1/4 tank issue (dont know who installed it). so.. im changing out the sending unit for a Fleece Sur-flo and eliminating the draw straw and modified sending unit. all rail pressures read good and no dtc codes so i believe this will fix it.