6.7 fuel pressure

[Jerry Powell]

I’ve got a 2013 6.7 deleted, EFI live, fleece cheetah, automatic that is having a bog/black smoke under hard throttle. You can put it on the mat, and it will bog, heavy black smoke, Rail pressure drop to around 2-3k, then pick up and take off like a rocket. All in a matter of probably 2-3 seconds It does it anytime you give it the slightest bit too much throttle. With my rail pressure dropping off like that is my fuel delivery pressure too low? Fuel filters are new. I’ve got the stock in tank lift pump. Any ideas?

 

[Jerry Powell]

Also, when slowing down to let a car in front of me turn, or approaching and red and slowing down and the turns green, any situation where I slow down to 15-30 mph and get back in it, it will smoke and bog then pick up and go. At lower speeds it will stay in 3rd gear when it really needs to shift to 2nd. In my opinion

 

[MtnRider]

Did this start when the tuning was installed or has it been running good with this setup and just started acting up? Black smoke is usually a sign of too much fuel so bad timing, bad injectors, bad turbo, etc?

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[Jerry Powell]

It’s been doing it for a little while. It only does it under hard Quick acceleration. If you ease into the throttle and roll into wide-open throttle it does perfectly fine. But you absolutely cannot quickly depress the throttle pedal. I can watch actual rail pressure and commanded rail pressure with my scanner and see the actual drop well below the commanded. That’s when it smokes and bogs down. I thought this was torque management causing this problem, but my tuner said that it was not.

 

[Jerry Powell]

I put the turbo on in January. Brand new

 

[Ozymandias]

Black smoke is always from over fueling, lack of Oxygen in the Cylinders. Either turbo spools to slow or tune ramps up fueling to fast and not according to charge air pressure.
Go back to stock tune and try again to rule out mechanical problems.

 

[Jerry Powell]

Ozymandias, I keep it on stock tune

 

[AH64ID]

Sounds more like a tuning issue. Stock power on a deleted tune doesn’t always mean stock tune.

I’d check with the tuner.

 

[Jerry Powell]

I have been emailing back and forth with the tuner, he’s saying fuel pressure as I have sent him data logs. but I haven’t heard back from him. I thought tuning issue first, then torque management but he said it all looks good on data log besides low rail pressure at initial acceleration.

 

[AH64ID]

Do you have a way to monitor lift pump pressure?

I still think tuning over lift pump pressure, as a data log could look good aside from low rail pressure and still be related to the tuning.

 

[Jerry Powell]

I don’t have any way to monitor lift pump pressure yet. I did switch back to the older software version this morning and it seems better, pressure still drops a little but it’s not near as harsh as it was.

 

[AH64ID]

Just saw your sig on EFI by Ryan, he's good. Not saying it can't be the tune, but he's among the better tuners.

 

[Jerry Powell]

Yeah it’s Ryan...I didn’t want to throw his name out there. No doubt he’s good. Im Just ready for my truck to be right. If it’s my lift pump starting to get weak I’d be perfectly happy putting an air dog on it but I just wanna make sure, don’t wanna spend that money if it’s not the problem

 

[MtnRider]

The fact that you saw some change with the change of the tune tells me it's not the lift pump. I would think if it's the lift pump it would be consistent since that is a fixed constant, It's not affected by tuning. Lift pump also doesn't explain all the black smoke either (unless it's just dumping fuel in once it comes back?). If anything I would think it would be starved for fuel if the lift pump was going out.
The only other thing I can think of is a failing fuel rail pressure relief valve or the tune is running the pressure too high? Maybe it's opening up dropping the pressure then dumping a bunch of fuel when it closes? With a change of tune maybe it's not running the rail pressure as high so not seeing it open as much? If not I'm still thinking tune or injectors?

I'm no expert so kind of spit balling a little bit but some of this seems logical to me given the symptoms you are seeing?


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[Ozymandias]

I don’t have any way to monitor lift pump pressure yet. I did switch back to the older software version this morning and it seems better, pressure still drops a little but it’s not near as harsh as it was.

That it drops a little going WOT all of a sudden is something I see to.
I think that is normal as the system needs a split second to ramp up volume and pressure.

 

[Jerry Powell]

Update, lift pump pressure is very healthy. No issues there. I removed and reinstalled the tune and it seems like it helped a little. Why I don’t know. Seems like a tune problem to me.

 

[Jerry Powell]

When installing the tune, do I need to have my csp switch on 1 and then install the tune? I always keep it on 2 which is the tow tune. Do I need to put it on 1 then upload the tune or does that matter?