P1689 Very hard to start after VP44 replacement and ECM reprogram

[skiracer0112]

Good morning, I bought what I thought was a good deal of a truck during the pandemic, a 1998.5 3500 auto dually. This forum has been very helpful thus far but I feel like I have hit a bit of a wall and was wondering if anyone had any suggestions before I go down too many rabbit holes. 

 

Currently my truck is showing a P1698 code, which can be cleared but immediately returns. It s very hard to start but will get going, rev and not throw the code when in park or neutral.  As soon as it is in gear and a load is applied the code pops and the engine derates. 
 

After installing the new vp44 it was running and staring very well. P1689 started suddenly on my way home one day about 300 miles after installing the rebuilt vp44 and has progressively gotten worse.
 

Repairs before P1689 issues started

Rebuilt VP44 from thoroughbred diesel last summer, tested this spring with a breakout box

Edge tuner removed

replaced grid heater relay, can’t remember code but bad circuit code popped

Repairs since P1689 started
Had ECM rebuilt and is installed with no change

Tested continuity between vp44 and ecm, all good but 14 ohms on ground

Cleaned all grounds on top of the motor

 

Thank you in advance!

[Silverwolf2691]

 

 

Hope this can get you started. Follow the instructions to the letter and it should get you some answers.

 

I think that 14 ohms to ground could be playing a part in this.

[Mopar1973Man]

2 hours ago, Silverwolf2691 said:

 

 

Hope this can get you started. Follow the instructions to the letter and it should get you some answers.

 

I think that 14 ohms to ground could be playing a part in this.

Yup I bet W-T ground mod will fix that.

[skiracer0112]

Thank you! I worked through that diagnostic to find the resistance in the ground at the vp44.  I started taking things apart for the W-T mod but thought I might ask first.  Especially since I have very limited experience with vehicle electrical systems. 

 

does the W-T mod address the ecm ground by the starter?

Edited July 7, 2021 by skiracer0112

[Mopar1973Man]

W-T ground wire mod address the ECM and VP44 grounds. They come from the passenger battery over. 

 

The ground behind the starter is fuel heater and lift pump ground.

 

 

[skiracer0112]

Great, thank you!  I had to go quite a few places to find the right parts but I have them all and will be performing to mod this afternoon. 

[Mopar1973Man]

 

New grounds for ECM and VP44...

Edited February 11, 2022 by Mopar1973Man

[skiracer0112]

Thank you to everyone for your help on this. Sorry I had not responded back sooner, the end of the summer got away from me and I haven’t been able to work on the truck much. 
 

I completed the ground relocation but the issue has persisted. I have noticed that the lack of power and the throttle cutting off is much worse when the motor is cold, and cuts out at 1500-1700 rpm. Once it warms up the throttle responds mostly normally, unless you really hammer it to over 2500 rpm.  A local shop took a look at it and they think it is a bad VP. Does anyone have any additional thoughts that I could try before removing the VP for warranty service?

[Haggar]

Ski,

That is how my brother's VP died.  It took us quite awhile to determine that it was the VP.  No codes.  We swapped ECM between my truck and his (both '01)  problem stayed with his truck.  The problem was when engine was cold, there would be no/little throttle response.  As the engine temperature increased (or fake engine temperature using heat gun on the vp) it would begin to run normally.   So we took the jump, ordered at VP from DAP and it has run normally since then.  Something in the VP was bad.  My hunch was the circuit board that drives the pump internally had resistances that changed as it warmed up.  Possibly cracked solders that were open/high resistance cold, but made contact hot.  Really don't know actual cause.

 

GL

HTH

Hag

[skiracer0112]

On 9/30/2021 at 5:30 AM, Haggar said:

Ski,

That is how my brother's VP died.  It took us quite awhile to determine that it was the VP.  No codes.  We swapped ECM between my truck and his (both '01)  problem stayed with his truck.  The problem was when engine was cold, there would be no/little throttle response.  As the engine temperature increased (or fake engine temperature using heat gun on the vp) it would begin to run normally.   So we took the jump, ordered at VP from DAP and it has run normally since then.  Something in the VP was bad.  My hunch was the circuit board that drives the pump internally had resistances that changed as it warmed up.  Possibly cracked solders that were open/high resistance cold, but made contact hot.  Really don't know actual cause.

 

GL

HTH

Hag

Thank you! That was what I was thinking could be the issue. Just was hoping for something else possibly. 
 

I pulled the pump yesterday and I think I figured out the issue. A while back I noticed that the vp mounting bolts loosened up, I tightened them and didn’t think much of it. However it looks like the key came loose when the mounting bolts did, so now I’m going hunting for the key in the timing cover or oil pan. 

[Haggar]

Wow,

Totally not what I expected!  Good luck!

 

Hag

[skiracer0112]

48 minutes ago, Haggar said:

Wow,

Totally not what I expected!  Good luck!

 

Hag

Not what I expected either!

 

Thank you everyone for your help in diagnosing these issues!

[Mopar1973Man]

The VP44 shaft nut should be torqued to 125 foot pounds. The 4 mounting nuts should be torqued to 32 foot pounds.

 

Always remember Dodge makes it, Cummins shakes it. Yup it takes some torque to hold it all together.

Edited October 4, 2021 by Mopar1973Man

[skiracer0112]

Thanks for the torque specs!  I was pretty sure I got it to those on the install, but I will be double checking this time for sure. The studs also backed out and I noticed when I pulled the pump that the threads were not in the best of shape so I plan to replace the studs and nuts as part of the process. 
 

the good thing also is pulling the cover will allow me to check and tab the kdp while I’m at it. 

Edited October 4, 2021 by skiracer0112