2014 Duramax

[Tuesdak]

It acts like there is a restriction in the fuel system from say a kinked hose or clogged tank sock. My favorite PIA repair was an internal hose flapper right at the injection pump inlet making the pressure gauges used read OK.

Plastic body Wix filters are known to suck air at the WIF threads. The filter head will crack and primer leaks are also common air leak failure points.

I assume you have checked the fuel for water and gasoline smell.

 

[TRAMPLINEMAN]

Is it possible in the meantime to jump out the sensor to get the vehicle running properly, and to use it as a diagnostic to see if the sensor is really the problem or not?

Yes, but it’ll be a few days before I can work on it.

 

[TRAMPLINEMAN]

It acts like there is a restriction in the fuel system from say a kinked hose or clogged tank sock. My favorite PIA repair was an internal hose flapper right at the injection pump inlet making the pressure gauges used read OK.

Plastic body Wix filters are known to suck air at the WIF threads. The filter head will crack and primer leaks are also common air leak failure points.

I assume you have checked the fuel for water and gasoline smell.

I’ve checked all the hoses and I can’t find any kinks or sharp bends.
I think when I install the Airdog I might eliminate the under hood filter.
Fuel smells good and there’s no sign of water.

 

[Ozymandias]

Keep it as a last defense, doesn't need regular change afterwards anymore but is there if something goes wrong somewhere else. More filter more safety.

 

[mpaulson]

Just a thought, did the CP4 have a check valve and this conversion CP3 not? If they even have one to begin with? Loosing its prime.

 

[TRAMPLINEMAN]

Just a thought, did the CP4 have a check valve and this conversion CP3 not? If they even have one to begin with? Loosing its prime.

I guess I really don’t know on the CP4. Guessing it’d be internal if so and I did not take the pump apart. On the CP3, we changed the inlet and return nipples as they were too small and installed the pump. This is the third one I’ve done and had zero issues with the first two. It’s probably something very simple I’m overlooking.

 

[Tuesdak]

Keep it as a last defense, doesn't need regular change afterwards anymore but is there if something goes wrong somewhere else. More filter more safety.

One keeps this filter head mess because of the WIF sensor and Fuel Heater. Otherwise it's rewired elsewhere with an aftermarket kit. I forget what years had the heater and it is a air leak point as well. Look for red black fuel heater wires on top of the fuel filter housing by the primer to know for sure.

When all else fails feed the engine from a 5 gal can/bucket with the return also in the bucket. This eliminates any possible problems with the tank and lines so you know where to look next.

 

[sag2]

That's right, but they are built from the beginning to run that way.

Here we have a completely different setup and a conversion to a Pump that wasn't meant to be in that environment she is now. And to make it worse it is computer controlled, just something slightly of from the programmed parameter can throw it into fault.

The CP3 conversion pumps have a mechanical lift pump built into the back of the CP3. It is a small housing attached to the back side with what looks like a cooling fins on it.

 

[TRAMPLINEMAN]

Thanks everyone for the comments, suggestions and knowledge. Dug into it again last night. Finished the Airdog install, bled the system and started the truck. Well, it didn’t go as planned. Still had the change fuel filter message, engine light and kinda stumbled. Prime the fuel system while truck was running and idle smoothed out, just like before. Turned the truck off, cleared the codes and restarted. Same thing. So, I decided to eliminate the fuel pressure sensor with the dummy plug kit I purchased and try again. Started the truck and it came alive. The idle was perfect, messages gone and sounded healthy. Put about 20 miles on the truck last night starting, stopping, normal driving and hot rodding and it never failed.
This morning, I called the brother of a coworker of mine who owns his own diesel shop. I explained the situation I’ve been having and he just laughed. He said he fought the same thing a while ago and has happened a few more times since when he’s done CP3 conversions with an additional lift pump. He said when the additional lift pump is added, he has always had to eliminate the fuel pressure sensor as it will now give false readings and derate power just like what was happening to me. Big lesson learned for me here, but if I never do another one of these I’ll be perfectly ok with it!!
Thanks again to those who responded.