Help With Intermittent Dead Pedal Diagnosis

[dillrepair]

i apologize for starting a new thread on this beaten to death topic especially since i know the info i'm looking for is out there,  ive read a few threads where moparman goes over a more foolproof diagnosis strategy for discerning between a dead pedal apps failure vs vp44 failure.    after searching for the last hour and a half i can't find the threads or info i'm looking for.     anyway my truck is 2002 ho 6 spd.   130k  nv5600.    edge jwa, with pressure gauge and egt installed and an analog fuel pressure gauge.    ddrp mounted on frame producing 17psi at idle and no lower than 9-10psi at wide open towing heavy.     

 

ABOUT A YEAR AGO:

so i'm going to paste some stuff from another post from last year on a different site to give some background:

 it all started in eastern WY driving up a hill. noticed CEL on and almost instantly after noticing light truck starts to run rough and loses almost all power, coast to rest stop luckily... truck is idling roughly... no power... will not start after shutoff. Normally i would have the tools to dx the situation myself but i'm in the middle of nowhere... middle of the night of course, no cell reception... payphoned the tow truck who comes and brings me to the official cummins repair shop in gillette. after some major bs with my aftermarket warranty company they say "warranty company won't pay but good news its just your DDRP lift pump thats failed please give us $500 to fix it all and that includes 2 hours of labor for diagnosis" i say FU sell me the lift pump and i'll go out in the ice and replace it myself... i relocated to frame rail for a reason. get back on my way east, CEL on again so i stop at autozone.. p0216 ... clear it and drive on. thing seems weaker going up hills doesn't want to make it over big hills and i felt it start to shudder again going up long hills, cel back on, i have no choice but to keep driving home.. make it all the way back to milwaukee and within sight of lake michigan dead pedal. idle it home. now the shop says they can't duplicate the problem, they got some apps code and something else but no p0216. (only reason i brought to shop is because i have stupid aftermarket warranty, who refuses at every turn to cover and i have to threaten lawsuit) 
installed at the time of initial failure was quadzilla xzt+ on highest setting, ddrp, 2002 ho 6 speed. any pointers would be great, sorry for the long story. shop says i can take it home and drive it for a while stock to get the problem to come back if i want and they'll keep the work order open? is there any other way to dx the problem without having it completely take a crap or throw a code? i was at the end of the warranty mileage during this trip and the drive down to the shop (with the truck acting surprisingly normal) took me to the end of my 12000 miles.

 

YESTERDAY'S EVENTS

so here i am... about a year later. got rid of the quadzilla xzt chip a while back and have been running and edge jwa on the middle/low setting for about 7 or 8 months with no issues. towed really heavy to move up north this past november with no issues. had a dead pedal again last night on the way back from my wedding. coasted to stop and turned truck off and on pumped pedal and it worked fine again. code 1693 and 0121 this time. i mentioned in an earlier post in this thread that i had seen the dreaded 0216 initially... which may or may not have been related to no fuel pressure when my lift pump died on that trip. when i took it to the diesel shop in milwaukee he drove it around for a week or so and they tested voltages on the pump itself and never found anything wrong. is this likely just apps then?

 

edit:  also since that whole ordeal last year i didn't experience any "loss of power" like i spoke of earlier.   and i'm not sure if thats an accurate description... what i may have been feeling was a flat spot up hills where the pedal wasn't producing any response... i'm just not sure. 

 

 

thanks again for the advice and sorry for the book. 

Edited February 23, 2014 by dillrepair

[LiveOak]

Perhaps you have read this before.  If so, my apologies.  If you had a P0216, your injector pump is on borrowed time.  It may run for another 20 years or die tomorrow. 

 

http://www.bluechipdiesel.com/vp44diagnostichelp.html

 

Sorry to hear you are having this problem.  I went through it a few years back myself. 

[dillrepair]

yeah i did read the blue chip stuff a while back but forgot about it till just now.   thanks.    and because i've only seen that code once right after my lift pump failed in wyoming i'm under the assumption that i still can have some hope its not the vp.    if it were i would assume that i would have gotten it again at least once in the last year, or had some power issues or something when towing heavy right?   i'm assuming that it would have gone to full advance towing a 20 foot trailer packed full of half an apt's worth of stuff up a steep grade or am i wrong?  

 

the vp44 had been replaced on this truck at some point before i bought it... judging by the remanufactured sticker on the pump.  (not that it makes any diff)

Edited February 24, 2014 by dillrepair

[Ilikeoldfords]

Since you are getting the 0121 code I am willing to bet that your APPS is gone. As for the 0216 code like said before, its probably short on time. Do you know how long it ran with no pressure? Sadly, if there was still any warranty on the injection pump, it was void whenever you lost pressure to the pump. You could get lucky though and have it run for another 20 years or not so lucky and only have another 2 days. Kinda hard to tell without the $600,000 test equipment though.

[dillrepair]

understood.  

 

as far as i remember it wasn't more than a few minutes that it ran without pressure.    it stuttered so bad i coasted up a little hill then down an offramp to a rest area luckily.      drove it today to the auto parts place to scan the code and to the hardware store,  both about 5-6 miles drive,  and there wasn't any noticeable difference in performance from before the dead pedal to now, maybe it even feels better than before i got that symptom.    i don't know what to say.     i had re-developed just about enough trust in the truck to think about ordering some rv275 injectors to finish off my mild increase in performance for the truck.... then this happened again.

 

i'm sure i'm in for another vp at some point.  the whole discussion about the vp44 is funny because really its all about when, not if, it will go bad.   so if it runs ok then leave it alone till it breaks.   everyone is due for another vp sometime but what i'm seeing as i read more and more is that some people are possibly replacing them when they don't need replacing yet.    

 

the shop in milwaukee i had gone too actually does have the expensive test stand for this pump,  they do a lot of work on cummins and one of the main guys there runs a vp rig himself, and they pulled competitively with one too for a bit as i understand.... however i don;t think they took my pump off and put it on the stand...    my assumption was that perhaps he would know if it was worth doing so and/or be able to test other voltages with the pump on the engine (as he claimed)  and make a decision if it was worth pulling, or had gone bad.        furthermore his decision to keep the truck and drive it himself for a week and half to see if the problem would repeat itself told me he understood the issue of diagnosing these issues that are fickle at times.     so anyway i took his word that my pump was ok after all the above.       maybe thats a bad assumption...  but like we said... every vp44 is going to go bad before we think it should.     

Edited February 24, 2014 by dillrepair

[dripley]

I had issues very similar to your after loosing my lift pump back in 2008. Dodge graced me with an in tank pump and a few months later I started having dead pedal issues and a little later some bucking issues. Turned out that the in tank pump was only putting out about 8 PSI at idle and less than 1 PSI at WOT. I installed a booster with the in tank pump and got the pressure up. This solved the dead pedal and the bucking issues. Ran that set up for 3 years. I finally replaced the VP and the two lift pumps about 3.5 years ago. The VP seemed to be running good but the earlier lift pump failure and exposure to the low pressures of the in tank pump stayed on my mind the whole time. I just decided to replace all of it on my time and not when the VP or lift pump decided for me. While your pressure aren't as low as what I experienced, they are lower than what I like. Currently I am running 19 and 15.5. I like the 15.5 PSI at WOT especially when towing(5th wheel at 15k) to allow for max cooling of the VP.