CP3 or Injectors????

[TonOfDalt]

Hello, im not new but couldnt remember my handle so I had to create a new one. I have been a member of the forum for a few years now however this is my first thread that is Diesel related....
So here is my issue.... Just picked up a Silverado 4-Door 2500HD with a Duramax/manual driveline for what I feel was a steal. I knew I was going to dump some money into it to get it going right but I wanted to get everyones opinion before I started spending. I believe my issue is either the CP3 or the Injectors. Here are the specs of the problem,
226,000 miles
Will not start without getting a shot of butane or being pop started
When cranking im reading about 400 PSI rail pressure... No joke! This is obviously why it wont start without more RPM than cranking
When at idle it sets the MIL and LIMP for a low rail pressure (about 2300 PSI) Doesnt die though
When given throttle the rail pressure seems to come right up and hold very close to whats being commanded
Seems that this LB7 is louder than it should be
Changed the fuel filter yesterday (found out what a pain in the arse air in the line can be, LOL!
Feels like it runs strong on acceleration/highway
Getting about 21 MPG

I have attached a log file...


To me this sounds like the CP3 but I dont want to spend more money than I have to fixing this issue so I would like to be more sure and get everyones advice.
If it is the CP3 does anyone recomend one pump over another (LBZ, ect). If so, what other mods do I need to make to make it work?
Does anyone recomend installing a lift pump? Auto Zone has one for $50 and I thought it might be a good buy just for the sake of priming.
Im not doing any major mods to this motor other than tuning. Not looking for big horse gains or anything so lets keep the suggestions in the right direction.
Thanks for any help!

[WisconsinHick1]

You might want to look into pulling the fuel filter head out. It might be loosing prime and bleeding off any pressure in the lines. Thats maybe why it keeps running after a little help. Does the desired and commanded fuel keep up to each other in the log? Sorry I'm not on my computer to look at it.

Also any surging while idling? You may consider putting in some two stroke oil in with your fill up as it is supposse to help quite it a little.

[TonOfDalt]

I know that when I removed the fuel filter when I changed it the old one was completely topped off with fuel so I am not so sure its that. As far as the log is concerned, the actual does keep up with commanded as long as the engine is not at idle. Once the engine is at idle then fuel pressure falls to about 2300-2600 PSI, almost half of whats being commanded. Last, there is no surging at any point.
Thank you

[THEFERMANATOR]

A bad CP3 will usually not hold rail pressure under load whereas bad injectors will not hold pressure at idle(or on a big tune). And injector return rate test is the ONLY test that will tell you which needs to be done. My bet would go on the injectors though.

[TonOfDalt]

That makes sense to me... Also would contribute to the noisyness of it from improper fuel atomization. How would I go about performing a return test?

[TonOfDalt]

Ok, so far from what I researched I think I have it all figured out however I just wanted to say that this is rediculous! You have to put in like 4 hrs just to be able to test the injectors???? Poor design in my opinion! It wasnt so bad to remove the top half of the valve cover but also the lower half too??? This sucks!

[WisconsinHick1]

You see if its an injector but not be able to pin point which one with less work. You can hook up to the fuel pressure return line off the heads. Drivers side is on the back side on top and passenger side is pretty much under the alternator. But like I said you can't pin point which injector is bad just that one of the four on that side is bad.

I think its anything over 5ml per injector after cranking 15 seconds the injector is bad so 20ml or more on one side one or more is bad.

[TonOfDalt]

Yeah, I was reading into that after I already started this endevor! LOL! I am this far into the driver side so I might as well just finish so I can be sure.

[TonOfDalt]

Quick update... I pulled the driverside injectors just to see what they looked like as I have never tore into a Duramax before and I found it almost looked as if the injecotrs where completely clogged with soot... Is this normal? All 4 looked about the same. Next, I started cleaning them up and I found the following stamped on the main body.... F468-O-6410 01-10-11 R
What would these numbers mean? Im thinking a part number followed by a date and then R for "remanufactured"
Any help would be great!