Fuel issue?

T

thepitts5

New member
I need some help figuring out an issue with my '08 6.7L. About a month ago it started stumbling after initial startup, but would quickly clear up. Then about two weeks ago it started missing once it reached operating temperature while in gear at idle, but will also occur when towing my bass boat. When it does it with the boat it literally jerks the truck. At first I suspected bad fuel, but I was able to rule that out after filling up with fresh fuel. I have done an injector kill test with no luck, basically it just gets worse as I kill an injector.

Fuel mods consist of AD II 165 (new filter), ATS duel fuelers (both pumps replaced 3 months ago) and 100% over injectors (about 9000 miles on them).

I have attached two videos, the first video shows the rail pressure (left) and lift pump pressure (middle). The second video is just for the audio.

Any thoughts or suggestions are greatly appreciated.

[ame]http://vid645.photobucket.com/albums/uu172/thepitts5/IMG_0160_zpsxvwbpk8c.mp4[/ame]

[ame]http://vid645.photobucket.com/albums/uu172/thepitts5/IMG_0161_zpstr6t4mdy.mp4[/ame]
 
Start with monitoring actual rail pressure vs desired rail pressure when this is happening. Will help at least narrow down your issue a bit.
 
Actual rail pressure jumps above the commanded rail pressure when it occurs, and then it commands less which causes it to stumble.
 
RP sensor and or FCA sound like a good place to start to me. Ideally a buddy would have same truck and you could swap temporarily so you don't have to spend money.

After that may consider sending injectors out for testing to confirm there are no underlying issues.
 
One or both FCA's? Possibly the dual pump controller? I considered the FCA,s, but I am assuming they are good considering both pumps are new.
 
Anyone have any thoughts on it happening because of the top pump being an LBZ? I remember reading something about having to make ECM adjustments if an LBZ pump was used in prior year Dmax's. My reasoning for asking is the original pump that came with the kit was an LB7 pump, so maybe the LBZ FCA is messing with the controller. If I buy a Cummins 6.7 FCA will it work, or would I need to buy a LB7 FCA? I really don't want to start buying random parts so any input is greatly appreciated.
 
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