Injection Pump or Pressure Regulator

[TonOfDalt]

I just finished replacing the DS injectors on my 02 2500HD ECSB LB7/ZF6.... The truck is running a lot smoother now but I know it still needs PS injectors. Thats going to have to wait for a bigger wallet though.... When I was logging and watching for any problems I noticed that actual RP was about 1000 PSI lower than commanded at idle and about 5000 PSI lower at highway speeds... I run EFI and when I tried to command a different pressure I got no change. To me this sounds like either the fuel pressure regulator or the injection pump... Any ideas?? Also... When cranking, the truck now gets up to about 1000 PSI of rail pressure which is about 400 PSI better than before the DS injector swap but still not enough to fire on its on. I either have to shoot it with Butane or pop start it to get the RPM's high enough to build enough rail pressure to fire the injectors...
Any help is greatly appreciated!:thumb:

 

[TonOfDalt]

Bump

 

[2500HeavyDuty]

try to command 160mpa using the dvt control in your scan tool.
if it wont come close its the cp3.

 

[TonOfDalt]

Thats just it though.... I cant get it to change no matter what I command.

 

[DAVe3283]

Thats just it though.... I cant get it to change no matter what I command.

Do any of the DVT controls work? A easy one to check is the Check Engine Light toggle. You should be able to force it on and off without trouble. If not, EFI may not be connected to the ECU correctly. Let us know if that works.

Sent from my Galaxy Nexus using Tapatalk 2

 

[Harbin_22]

Unplug the regulator and see if it goes up

 

[TonOfDalt]

DVT controlls work fine, I can command any idle speed, injectors, MIL, anything I want just no change when I command rail pressure.
I am in for the night but I will try unplugging the regulator tomorrow and reply with my results.
Thanks guys

 

[TonOfDalt]

Ok, I unplugged the regulator and got no change in pressure. It would do the same thing as before and raise with RPM but still about 5000 PSI short at 2200 RPM and 1000 short at idle.
I thought maybe the regulator is just stuck in a certain position so I hooked it back up and tryed commanding a lower RP. Sure enough, after a few seconds I saw rail pressure dropping quick and it started to die untill I re-raised the commanded. So I believe the regulator is fine. Looks like I have a weak pump.... or the PS injectors are so bad that its not allowing the pump to build the pressure it needs.
I guess I am going to finish replacing PS injectors first as I know it needs them from a return test performed. I am supposed to be coming into a chunk of money in the next week or so, that being said... I think I might just go ahead and replace both at the same time to save me some headache. I will post on how it goes.
I am going to be posting a new thread "What CP3 should I buy" to get some ideas on where to go on that topic.
Thanks for all the help! :thumb:

 

[Burn Down]

If you already did the injector return test and the driver side is returning to much fuel, I would bet thats your rail pressure issue... How far out of spec was the passenger and drivers side injector return?

 

[TonOfDalt]

If you already did the injector return test and the driver side is returning to much fuel, I would bet thats your rail pressure issue... How far out of spec was the passenger and drivers side injector return?

Rates for both sides where double the maximum GM factory spec. After replacing the injectors on the DS my RP while cranking went up 200 PSI. I am sure that this is now making the PS injectors scream! I am almost sure that replacing the PS injectors will solve my starting issue however I am sure the pump must be on the outs as well because like I said, when I command max pressure, there isnt even the slightest bit of change.
Thank you for the help

 

[Burn Down]

I doubt there is anything wrong with the pump... Double the return rates on one side would most deff. cause a serious low rail pressure problem. Your FPR sounds a little suspect. If you still have issues after the injectors I would look at the FPR before I did the pump. Some guys swear by the 2-stroke oil trick of freeing up FPR's and injectors... I don't know if it works or not? But hey it's cheap so why not?

 

[TonOfDalt]

I doubt there is anything wrong with the pump... Double the return rates on one side would most deff. cause a serious low rail pressure problem. Your FPR sounds a little suspect. If you still have issues after the injectors I would look at the FPR before I did the pump. Some guys swear by the 2-stroke oil trick of freeing up FPR's and injectors... I don't know if it works or not? But hey it's cheap so why not?

Well, I have been alternating between ATF Fluid and Diesel Kleen on fill-ups... I will try some two stroke next fill-up to see if that helps the situation at all. Appreciate all the input!

 

[Burn Down]

Well, I have been alternating between ATF Fluid and Diesel Kleen on fill-ups... I will try some two stroke next fill-up to see if that helps the situation at all. Appreciate all the input!

Your still driving it? You have to be making more than 5,000 psi of rail... I don't think it would hardly move at 5K. If you have been running all that through it, I doubt the FPR is sticky. Get the rest of your sticks done and report back.

 

[Burn Down]

Oh and stop using injectables to start it, your going to break something if you don't do it right...

 

[TonOfDalt]

Lol, I think you read over the part where I said "5000 below requested @ highway" RP climbs with RPM. But it still does not even change a single bit when I try to command different no matter what the RPM.

 

[TonOfDalt]

Not to worry, I use a very small shot of butane. Just enough to get the RPM's up enough to raise pressure. When I do this I am sure to not use so much as to cause a ping or over idle speed. This is my first duramax experience but by far not my first rodeo. Been wrenching for about 15 years now on anything GM. :thumb:

 

[TonOfDalt]

Well, it looks like I am going to be able to order the PS injectors Thursday and hopefully will have them on Monday. I am also hoping to score a LBZ pump in time so I can install them together and save myself the tear-down time. I will keep posted.