stumble on acceleration

[Thunder2001]

Just came in from looking at it and ran it and watched the scan gauge. the scan gauge and few dash gauges were suprisingly both accurate. the tps reading seemed riight on with pedal position except in the display you could see small traces of a number1 flashing next to the number. Almost looks like it is supposed to do that.  It is real cold out there today but I want to rig up a test fuel supply to rule out the lift pump completely. Doug at Blue Chip said it wouldn't hurt the VP as long as I didn't do it long. I shut the engine off and checked the APPS reading with the pedal movement and it goes from 0 to 99% smoothly.

[dripley]

I believe everyone sees that little blip with the # 1 flashing. OI now mine does. The scan gauge should match the dash gauges it is getting it's info the same as the ECM.

[Thunder2001]

I do have a guy that has all the good scanners but would have to make an appointment. He is one of those techs guys with no mechanical skill. Kind of like the commercial where he can't fix it but he just tells you it is broke!

Is the stock lift pump powered directly from the ECM? I looked at the wiring diagram and it shows the power side of the pump going straight to pin 35 and 15 of the ECM . I thought the ECM would control the  fuel pump relay to then power up he lift pump. I could see this to be a problem especially if the Air Dog has  a high draw.

Edited February 9, 2017 by Thunder2001

[JAG1]

Right. Make sure the lift pump is powered from the battery thru a relay controlled by the ECM. Don't let the ECM power it like it was set up from the factory originally.

Edited February 10, 2017 by JAG1

[dripley]

The lift pump does not have a relay. The fuel relay in the PDC is for the VP.

[CLAUS1]

your air dog should have came with a Relay and wiring harness that ties into the factory lift pump connector and than run the other 2 wires to the battery

 

[dripley]

I dont believe the Raptor pump comes with the wiring harness. They just plug right into the oe harness.

Edited February 15, 2017 by dripley

[JAG1]

1 hour ago, dripley said:

I dont believe the Raptor pump comes with the wiring harness. They just plug right into the oe harness.

That is the way I think it is too. I had to buy a Harness and relay and install it correctly. I carry an extra relay with me for good measure.

Edited February 15, 2017 by JAG1

[Dieselfuture]

9 hours ago, dripley said:

I dont believe the Raptor pump comes with the wiring harness. They just plug right into the oe harness.

@ Raptor pump

[Thunder2001]

Yes you are right about the pump, so I have made a relay and harness and am going to see if it helps. I am just waiting on my Big Line Kit and proper fuel pressure gauge to come from Vulcan. I just want to eliminate any possible problem before I run it again. I will be very disappointed if after all this, that it ends up being another faulty VP. I will report back as soon as I run it again.

[dripley]

I have been pretty lucky with VP's. My first one failed at 75k and it was replaced under warranty. I replace that at 217k. It actually survived a lift pump failure and then I dont know how many miles on an in tank pump producing little to no pressure. Replaced that one with a Blue Chip pump just like yours. 175k miles later and it is still going strong.

[JAG1]

It still amazes me how much Dodge engineers didn't bother to design the fuel system to take care of the VP's requirements.

 

Maybe there was no engineer on it. When Dodge first used the 24 valve, Cummins must have sent some fuel spec. requirements for the Bosch VP44. Was Dodge negligent? I don't know. 

[Me78569]

Honestly I think most of the VP44 failures were related to the actual deisgn of the vp rather than input fuel shortcomings.  

 

Things like

-non-leaded soldier coming into play

-bad hardness in the timing piston

-change to ulsd fuel in the middle

etc. 

 

I would wager that later revision vp44's would live a long happy life with very little inlet pressure.  Obviously we want to try and make them last as long as possible so we kepe pressure up lube the fuel etc.  

[Tractorman]

On ‎2‎/‎15‎/‎2017 at 9:07 AM, Me78569 said:

Honestly I think most of the VP44 failures were related to the actual deisgn of the vp rather than input fuel shortcomings.  

 

Things like

-non-leaded soldier coming into play

-bad hardness in the timing piston

-change to ulsd fuel in the middle

etc. 

 

I would wager that later revision vp44's would live a long happy life with very little inlet pressure.

 

I very much agree you and here is why.  I am the original owner of my 2002 truck.  The VP44 and lift pump were replaced in 2005 at 87,000 miles under warranty for timing piston failure code on the VP44. 

 

The lift pump pressure was in specs before the VP44 and lift pump were replaced.  I drove the truck for a week (50 miles per day before I gave the truck to the dealer)with a fuel gauge attached to my windshield wiper and the fuel pressure always stayed within specs under all driving conditions. 

 

After the replacement of the VP44 and the factory modification of installing an in-tank lift pump, I installed the same fuel pressure gauge and fuel pressure was much lower than specs under all driving conditions (6 psi at idle and 3 psi under a load).  I questioned the dealer mechanic (a very knowledgeable guy)  about this and he said he is aware of this, but the new lift pump installation change is required by Dodge. 

 

Fast forward a few years - I currently have 267,000 miles on the truck (180,000 miles on the replaced VP44).  In the spring of 2016 (at 251,000 miles) I replaced the in-tank lift pump (which was still working) with a frame mounted used FASS lift pump.  I only did this in case the lift pump failed while on a road trip which would make for an easy repair. 

 

So the VP44 ran for 11 years and 164,000 miles with the in-tank lift pump operating at very low pressures and the VP44 is still running fine.  Hmmmm....

 

Thanks for listening

 

- John

Edited February 19, 2017 by Tractorman
grammar

[Thunder2001]

Yes you are right about the pump, so I have made a relay and harness and am going to see if it helps. I am just waiting on my Big Line Kit and proper fuel pressure gauge to come from Vulcan. I just want to eliminate any possible problem before I run it again. I will be very disappointed if after all this, that it ends up being another faulty VP. I will report back as soon as I run it again.

Well I have installed the Vulcan big line kit and the relay for the lift pump. I also installed a mechanical fuel pressure gauge. These changes made no difference in how it runs. I will post another video sometime today just to show you guys. The only thing left is maybe the waste gate is stuck open? Would that cause a stumble under load? I don't even want to drive it like this for fear of not making it back. Just an example of what happens, If I try to create a driving load by doing a small brake torque, it will just stumble till it dies. Also I did check for AC voltage and had a maximum of .012 volts. Running out of ideas and thinking maybe a second bad VP 44. Doug from BlueChip said sometimes the electrical parts are like light bulbs and they are bad out of the box. Maybe both these light bulbs came from the same box?

[Thunder2001]

Update 2/24/2017.  Here is the video I said I was going to post.  Let me know your thoughts.

 

[Me78569]

edit just reread everything.   

 

Thinking. 

 

 

I really wish I could see the canbus data and see if the ecm is sending junk data for some reason.  

 

 

Edited February 25, 2017 by Me78569

[Thunder2001]

The APPS is brand new and I did do the proper reset on it. Last time I checked, the tps  numbers seemed to be moving smoothly along with pedal movement. Seems slow on the video because I think the scan gauge might have a slight delay when throttle is pushed. 

[Me78569]

I almost wonder if you have a corrupt fueling table in the ecm.  

 

Is anyone local a smarty you can flash then flash back?

[Thunder2001]

Would the can bus data come from the ECM ? If so this is a fresh ecm and it is doing the same thing the last ecm did. Also would the PCM have anything to do with this? The PCM is one of the only original parts left on it. one more thing is that my harmonic balancer looks bad but I didn't think that it could cause this problem. Sorry about my poor typing skills, I am learning as I go.