CAT C15 /6NZ trouble continues

do you have any thoughts on what a guy can do to keep it from happening again? I do a lot of heavy haul.

 

No, I do not. It seems to make more of an issue, after injectors are removed and reinstalled. That removes the carbon seal, that forms on the injector tip. If there is too much leakage at the seat, it doesn't get a chance to build up again.

 

when you perform the repair, are you making the seats deeper or larger for a better contact area, or just truing them up?

 

Just truing them up.

 

got it.

I think I'm going to baby it for a month or so, keeping my foot out of it in the high boost rpm range. hopefully it will get a chance to build some carbon around the tips to help seal the seats somewhat before I start pouring the coal to her.

thank you for your posts and information, it is certainly appreciated.

 

Is this the reason that in 2004 the BXS engines used an O ring near the injector tip?

 

here is a video of what my truck was doing, the shaking is quite evident until the affected injector kicks in again. the boost gauge is center of the far left row, as soon as the missing stops the boost pressure climbs.

 

that is quite common in early stages of injector failure. sometimes caused by a sticky rotary actuator or sometimes by grooves worn into the armature plate under the solenoid. the spring under the shim in the middle of the armature plate can catch on the grooves rendering the solenoid useless until the spring comes free.

typically first stages of failure under load are intermittent short length misfires under heavy load when you grab 1/2 a gear on a big pull. they start with short misfires that self correct. generally then the driver says it will keep missing until he lifts off throttle completely and re-applies it. then the next complaints are that the misfire will stay for a decent period of time on a pull and no driver action can make it fire again until it does it itself.

cutting out a cylinder on the dyno under load generally drops 100hp to the ground instantly and bucket loads of torque.... hence RPM drop and boost drop.

this can also be caused by blocked primary fuel filter, bypassing injector orings or as you are discussing carbon/combustion back into the injector sleeve. I feel lots of techs don't properly clean the sleeve or tip seat when changing an injector. they just give it a wipe and fit the new one with the tip and oring sealing against old seal and carbon build up.

I have had a few reman and a few built locally do exactly what that video shows. none of my problem ones were caused by carbon bypass though. all from actuator or armature plate spring and shim bore

 

well I'm hoping the new injectors and head will be the cure. my symptoms may have been a combination of things, but everything had been gone through before the parts mentioned were replaced. fuel pressure checked, filters, fuel lines, electrical connections, everything short of removing the injectors. cat had a bad batch of reman injectors as mentioned by Dan (the OP) and that's the info that got me to the point I'm at now. Cat agreed to warranty the injectors and then the head after the obvious injector seat failure evidenced by the condition of the reman injectors from the platinum in frame.

just to add, no amount of lifting off the throttle and re-applying would make it stop. and as the engine heat increased, the length of time the missing would occur would also increase. when the truck was cold it never missed a beat and you couldn't make it miss at all, until under load and heat soaked. I should also add, this missing has been happening for several years after the in frame, and getting progressively worse.

the only thing I wish the tech would have done during his ride along with the computer hooked up was the injector cut out test while the missing was happening so it that we would have known exactly which jug was missing. was it a different hole doing it each time, or the same one...and why, if it was leaking combustion so badly, would it only occur when hot? so many questions, so little answers.

had it out the last 2 days pulling 32 wheels hauling a 350JD excavator and so far so good...keeping my fingers crossed.

 

any updates Dan?