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Duramax Fifth Generation: 2011-2016 (LML) Discuss the fifth generation (2011-2016) of the 6.6L Duramax diesel engine & associated components. Engine related discussion ONLY.

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Old 05-02-2018, 08:36 PM   #1 (permalink)
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Possible cp4 failing

Hey guys new to the forum, I have a 2016 lml ppei ezlynk tuned with 5” exhaust, fass 165gph. I was driving home from North Carolina and I started having power loss during acceleration or any time I was on the throttle but idles fine. My injection pressure drops at any KPSI then I let out of the throttle and if I gradually get back into the throttle it works for a few seconds then back to dropping KPSI. I’ve checked my fittings, filters and lines from my fass and everything looks good. I rebuilt my stock filter head and it didn’t help. I removed the stock filter head and by passed it with a hose and two hose clamps. Still having the issue. I even put a full tank of fuel in it just to make sure I wasn’t have a quarter tank issue. I have yet to pull the fpr as I’m not a mechanic just like tinkering on my own trucks. Wonder if anyone else ever had these same symptoms and what did it end up being? Also truck will basically stall out trying to climb hills!

2016 LML Duramax
ppei ezlynk tuned with 5 exhaust, fass 165gph
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Old 05-03-2018, 12:11 AM   #2 (permalink)
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Join Date: Jun 2015
Location: Kadina, South Australia
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Do you have any codes?

Have you checked that the FASS is actually pumping fuel? You may have a bad FASS or maybe the 165 is having trouble getting the required supply from the tank if you're still using the factory drawstraw system.

I have a FASS 150 and was a bit paranoid that the stock drawstraw might not be big enough to supply enough fuel for that thirsty FASS. So, I installed a Beans Sump and now have a direct 1/2" hose with no chance of any hiccups from the tank to the FASS.

I don't think it would be a CP4 issue (yet) because from my knowledge of the CP4 it either works or it doesn't... no in-between with that sucker!!! However, if the FASS or some other problem is causing the CP4 to starve for fuel, then THAT is what may lead to a CP4 failure. I'd get to the bottom of it asap!!!

Good luck,

Kadina, SA

2012 LML Duramax LTZ Crewcab. CSM canopy.
Full delete.
6" Procomp lift plus air bags
Mickey Thompson 305/70/R18; twin spares.
TUFF bullbar.
FASS 150 lift pump/filters + back-up Kennedy lift pump.
Bean's fuel tank sump kit. Titan 57 gallon tank.
Banks 4" straight thru exhaust and cold air intake.
Fyrlyt Nemisis 250 watt spot lights
Front, side and rear LED bars.
Extra 100a/h battery in back to run 60 litre fridge.
PX07 air compressor and 18 litre tank.
3 sets of air horns.
EFI Live tunes (using TOW tune)
AirSafe Hitch
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