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P1689 Very hard to start after VP44 replacement and ECM reprogram

skiracer0112
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skiracer0112

skiracer0112

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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!

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skiracer0112

skiracer0112

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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 by skiracer0112
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  • 2 months later...
skiracer0112

skiracer0112

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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?

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Haggar

Haggar

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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

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skiracer0112

skiracer0112

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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. 

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skiracer0112

skiracer0112

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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 by skiracer0112
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