APPS or Injection Pump

[Jimmy0611]

I have a 1999 2500 with 165,000 miles. I bought the truck 6 months ago with fuel issues taking a chance. It would take partial throttle before cutting out. It had a cheap aftermarket pump on the rail (no name) that had recently been replaced. I immediately ordered a FASS titanium lift pump and b&d sump. I removed the factory fuel filter setup. The truck ran fine With zero issues until a month ago. I filled up, drove 60-70 miles and came home. The next day the truck started to have an intermittent dead pedal. Seems to be only at cruising speed, never during acceleration. 
 

Fuel pressure with key on not running is around 18psi so lift pump is fine. Fuel pressure at lift pump is 15-16psi under a load. When truck starts acting up, the fuel pressure gauge will bounce between 12-18psi rapidly then if i let off the throttle and get back in it, it usually clears out.

 

There were no active codes with my Innova scanner but my friend used a Snapon scanner and pulled TPS high voltage code. I checked +V input signal on MAP, oil pressure, and CAM sensor and getting +4.57. I have checked continuity between all 6 TPS pins and their correlated pin on the ECM 50 pin plug and continuity is there. Signal voltage on APPS was +5.27 and +3.65 with accelerator pedal fully depressed. I adjusted TPS to factory spec printed on sensor which was +5.85, did the APPS reset and now truck had constant dead pedal. 
 

I am at the end of my rope. I have taken this as far as my limited diesel knowledge allows me. What else can I check before becoming what i despise most....a parts changer. Any help would be appreciated

 

[wil440]

If your friend has a newer SO scanner get it and check APPS through it's range using the live data function, apps voltages should change smoothly up and down in relation to pedal with no hiccups, when mine failed it was very intermittant and would be fine for days then really have a fit, wasn't very old... fitted by PO and of course made in ..... china. If it is APPS get a timbo off of this site, I didn't as I didn't know about this forum then 

[Jimmy0611]

Checked apps through range, slowly. Zero bad spots, all smooth. 

Edited July 8, 2020 by Jimmy0611

[wil440]

Have you ran through the diagnostics for apps voltage high ? In OBDll in 24v articles.... sorry can't link on my phone or I'm too dumb to figure out how ☺  also did you check apps output with engine off ign on and then running to compare. Also now its total dead pedal is there different codes or still the same

Edited July 9, 2020 by wil440

[Mopar1973Man]

5 hours ago, wil440 said:

Have you ran through the diagnostics for apps voltage high ? In OBDll in 24v articles.... sorry can't link on my phone or I'm too dumb to figure out how ☺  also did you check apps output with engine off ign on and then running to compare. Also now its total dead pedal is there different codes or still the same

 

I will help you out...

 

[Jimmy0611]

Recalibrated tps (again), did APPS reset (again), and truck drove fine. However, now Im getting p0216 code...I already know what that means. Thanks for all the tips, I enjoy learning.

[Mopar1973Man]

Low fuel pressure and failed timing piston in the VP44.