Difficult to diagnose. 2002 2500 several problems.

[Tdubnrp]

So I inherited this truck from a family member and im not well versed in diesel engines/mechanics. Here are the issues im having and then i'll explain what has been done to the truck so far.

1. Wont exceed 2000rpm. From what ive read its in "limp mode". It will drive, and if i ease off the accelerator it will shift and I can get up to 60-65mph. However, it will shift but wont shift to its full potential.

2. When the engine is idle or stopped at a red light, stop sign, etc it will die. If I put it in neutral and milk the throttle though it wont die.

Heres what I know has been done to the truck lately to fix this issue.
-Lift Pump
-Air filter
-Injectors changed
-Batteries changed
-Brand new OEM trans
-Glow plugs changed

If anyone has any suggestions, please. PLEASE let me know. The only conclusion I can come to is the CP3, but I cant see how the truck can run as well as it does if thats the case. Maybe im misunderstanding its complete function?

 

[TheBac]

Codes?

 

[jlawles2]

What does it sound like, i.e. old tractor, sounds normal? Lift pump putting out, did you change under hood filter? Check the harness plugs on top of the engine to see that none of the pins are pushed back.

As mentioned check engine light and codes? How many miles on the truck? Does it have a tune on it or a tuner box of any sort? If so, those are first to be suspect.

Who installed the trans? If tuned and someone went in and flashed the ECM when they did the trans funny things can happen.

Before you change the CP3, check the rail pressure (how is up to you to figure out). CP3 are not bullet proof, but FPR are known to go out before CP3 and that can cause odd issues.

One other odd thing would be to open the exhaust up between the downpipe and the front pipe in case there is an exhaust obstruction that is killing airflow.

 

[2004LB7]

As Tom said, if it is in limp (2k rpms) then there should be codes. It's a shot in the dark without them

 

[Tdubnrp]

I'll have the codes shortly, I was just able to get a doodad to plug it up and ill post it back here. So In regards to @jlawles2 mileage is in the low 300's range im not exactly sure. According to family the trans was done by a professional shop somewhere local, and the truck isnt tuned. Also i have no idea what "rail pressure" is or how to check it. I can definitely check that exhaust though. As far as the way it sounds, to me it sounds perfect, like a normal diesel engine. It isnt rough or whiny like some videos ive seen.

How can I check if the lift pump is pumping correctly? The under hood filter was changed as far as I know. Supposedly this truck was well taken care of before this issue started and apparently the mechanics it was brought to couldnt figure it out. I really wish I could give you guys more info. This is just beyond any knowledge I have. Im a nerdy tech paramedic lol. Diesels are fascinating to me, but im really stupid when it comes to mechanics.