2014 Duramax

[TRAMPLINEMAN]

I did a CP3 conversion on a ‘14 Duramax over the weekend. I drove the truck afterwards for about a half hour and turned it off, truck ran great. When I started it up, it was sputtering and would not move under its own power. I got a “change fuel filter” message on the dash. This was a brand new filter, but after I had it towed home, I put another new filter in. Same thing, truck sputters and “change filter message”. Hooked a scanner up and reset the filter life from 0% to 100% and it immediately went back to zero. Tried this many times and it always returns to zero. I’ve rechecked every connection, harness, plug in and fuel line many times, everything is as should be.
Anyone have any ideas?

 

[Ozymandias]

Did you disconnect the battery's during the process?
So it starts with a blank memory on factory values.

 

[TRAMPLINEMAN]

Did you disconnect the battery's during the process?
So it starts with a blank memory on factory values.

Yes we did.

 

[BigPapa]

Genuine filter or Chinese counterfeit?

 

[TRAMPLINEMAN]

Genuine filters.

 

[Ozymandias]

Can you measure the pressure from the lift pump? Does it flow enough?

Do you need a different ECM tune like Ram does for the CP4>CP3 conversion?

No fault codes from the ECM aside from the filter full message?

 

[TRAMPLINEMAN]

Can not measure lift pump pressure, as these Duramaxs do not have lift pumps. But, we have an Airdog on its way.
This pump kit is no tuning required. We told them what we had and this is the kit they recommended. They said the kit that requires tuning is for trucks that are or will be modified.
No other codes are present, just the “change fuel filter” message.

 

[BigPapa]

Maybe???

 

[BigPapa]

There is also this one, but, I think it was superseded by the one I posted above.

 

[Ozymandias]

Well I think there we have it, the CP3 "can" run without a lift pump but it definitely does not like it, especially if the tank is so far away, so much lower and through a restrictive filter.

I'd say after you have put on the Pump the problem will be gone.

Edit: because all the symptoms you have point to fuel starvation.

 

[TRAMPLINEMAN]

Maybe???

View attachment 141544

I will go thru it all again, thank you.

 

[TRAMPLINEMAN]

Well I think there we have it, the CP3 "can" run without a lift pump but it definitely does not like it, especially if the tank is so far away, so much lower and through a restrictive filter.

I'd say after you have put on the Pump the problem will be gone.

Edit: because all the symptoms you have point to fuel starvation.

Maybe that’s the reason there’s been so many CP4 failures, no lift pump?!
I do feel it’s a fuel starvation issue. When it starts to stumble, we pump the primer a bunch of times and it smooths right out and will idle perfectly fine.

 

[TRAMPLINEMAN]

Maybe???

View attachment 141544

I read somewhere that these trucks have issues with the fuel pressure sensor between the filter and injection pump. If the faulty sensor reads too much vacuum it will display the “change filter” message and truck will stumble into reduced power and won’t allow the filter percentage to be reset. These are the symptoms I’ve been having. I ordered the sensor delete kit, should be here in a couple days. Was told by two different shops to delete it being it’s a known problem and the Airdog has an adjustable flow rate on it.

 

[BigPapa]

None of our 600+ 6.7L Cummins powered school buses have a lift pump. We have replaced 25 HP Pumps on them over the past 8 years. I dare say, half of those PROBABLY only needed and actuator, not the pump.

 

[Ozymandias]

None of our 600+ 6.7L Cummins powered school buses have a lift pump. We have replaced 25 HP Pumps on them over the past 8 years. I dare say, half of those PROBABLY only needed and actuator, not the pump.

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.

 

[Ozymandias]

By the way, what was the reason for the conversion?

 

[TRAMPLINEMAN]

By the way, what was the reason for the conversion?

The truck owner was told by someone that it needed to be done before the CP4 grenaded and took out the whole system. There was no changing her mind.

 

[Ozymandias]

The truck owner was told by someone that it needed to be done before the CP4 grenaded and took out the whole system. There was no changing her mind.

Good, so it didn't fail sending debris throughout the system then, I had that in mind.

We'll see how it behaves once the AirDog is installed.

As a note, id leave the pressure sensor alone for the moment if the Pump solves the problem.
It can still work as a filter minder in the future.

 

[TRAMPLINEMAN]

Good, so it didn't fail sending debris throughout the system then, I had that in mind.

We'll see how it behaves once the AirDog is installed.

As a note, id leave the pressure sensor alone for the moment if the Pump solves the problem.
It can still work as a filter minder in the future.

Nope, it hadn’t failed yet.
Yes, I planned on leaving the sensor in until we installed the pump.

 

[Signal73]

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?