02 lb7 low actual rail pressure, any advice would be awesome! - Chevy and GMC Duramax Diesel Forum
01-04.5 LB7 Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

 
LinkBack Thread Tools Display Modes
post #1 of 9 (permalink) Old 01-11-2020, 06:30 PM Thread Starter
 
Jamieslb7's Avatar
 
Join Date: Jan 2020
Location: Springfield, Ohio
Posts: 2
02 lb7 low actual rail pressure, any advice would be awesome!

Hey, I’m new to this forum but have found a ton of great info. I recently bought a 02 gmc 3500 and realized it has low fuel pressure it has trouble getting over 40 MPa at wide open throttle. I also noticed on my scan tool the commanded fuel pressure regulator was really high. I just need some advice if I should be budgeting for a new cp3 or fuel pressure regulator or both? My truck feels like Godzilla has ahold of the back bumper lol Thanks y’all for your time. I attached a screen shot was I was seeing on the scan tool.
Attached Images
File Type: jpg 3A7D16D3-F1B6-4AC9-B760-373FDE9BC477_1578792515381.jpg (21.6 KB, 50 views)
Jamieslb7 is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 01-11-2020, 06:38 PM Thread Starter
 
Jamieslb7's Avatar
 
Join Date: Jan 2020
Location: Springfield, Ohio
Posts: 2
Sorry forgot to mention I put on a new air dog 100 and new k&n fuel filter along with new seals in the fuel head.
Jamieslb7 is offline  
post #3 of 9 (permalink) Old 01-18-2020, 02:53 PM
Duramax Lifetime Supporter
 
stevewaclo's Avatar
 
Join Date: Aug 2012
Location: Carson City, NV Proud Participant, Federal Witness Protection Program
Posts: 656
Try this

Hello and welcome!

A chronic problem with LB7 injectors is trouble with the ball and seat in the internal return circuit. One or more may become badly worn and instead of the typical return flow, diesel fuel is hydraulically “short circuited” and correct rail pressure cannot be established.

A simple test may be done by going under the truck and disconnecting the return fuel line between the fuel cooler and tank (often impossible due to corrosion, so cutting in is necessary) and measuring fuel return flow into a container with the FICM fuse pulled and 15 seconds of cranking.

The test may also be performed topside on a bank-by-bank basis, but I believe if total return is incorrect, just do all injectors at once.

Consider SAC vs VCO’s.

Search the forum for specifics and a better pic of injector innards.

Other issues may cause low rail pressure, but this is often low hanging fruit.
Attached Images
File Type: jpg 4D40D833-FD18-4469-A962-AFC2E7C5FB9D.jpg (21.1 KB, 28 views)
File Type: jpg F77963F3-51AF-474E-8A59-3AB352BBE640.jpg (21.4 KB, 28 views)

2003 GMC Sierra 2500HD SLE ExtCab CA Emissions; 155k; Allison 1000 w/Transynd X2 Flush & Fill; 8' bed; AFE/CAI; MBRP 4" Exhaust; Side Tint, 33% VLT, rear, Limo; Smittybilt Stainless Side Nerf Bars; Sprayed-in Bed Liner; MadJack Fuel Filter Access Door; Regular Used Oil Analysis (latest available on request), Blackstone Labs; EGT/Boost Gauges; Dual Chrome Dipsticks, JC Whitney; Stainless Steel fuel filter head bleeder screw; New WP and Hydroboost; Billet Aluminum Fuel Filter Housing Spacer; Professionally repaired instrument cluster (new steppers and lamps); Does anybody ever read this s%#t?; Injectors under warranty @ 70k; 2nd set DIY @ 155k
stevewaclo is offline  
Sponsored Links
Advertisement
 
post #4 of 9 (permalink) Old 01-18-2020, 08:08 PM
Duramax Lifetime Supporter
 
stevewaclo's Avatar
 
Join Date: Aug 2012
Location: Carson City, NV Proud Participant, Federal Witness Protection Program
Posts: 656
Better injector diagram

Here’s a better diagram. Note ball.
Attached Images
File Type: jpeg 552A3CEA-66E5-41EF-8EEC-71FA57C18328.jpeg (45.5 KB, 25 views)

2003 GMC Sierra 2500HD SLE ExtCab CA Emissions; 155k; Allison 1000 w/Transynd X2 Flush & Fill; 8' bed; AFE/CAI; MBRP 4" Exhaust; Side Tint, 33% VLT, rear, Limo; Smittybilt Stainless Side Nerf Bars; Sprayed-in Bed Liner; MadJack Fuel Filter Access Door; Regular Used Oil Analysis (latest available on request), Blackstone Labs; EGT/Boost Gauges; Dual Chrome Dipsticks, JC Whitney; Stainless Steel fuel filter head bleeder screw; New WP and Hydroboost; Billet Aluminum Fuel Filter Housing Spacer; Professionally repaired instrument cluster (new steppers and lamps); Does anybody ever read this s%#t?; Injectors under warranty @ 70k; 2nd set DIY @ 155k
stevewaclo is offline  
post #5 of 9 (permalink) Old 01-24-2020, 01:37 PM
 
Join Date: Jan 2020
Posts: 3
Hey also new here. I have the same problem. First noticed it when I put an edge insight on it, wont get above 9kpsi. Immediately put a airdog raptor 4g on it to see if it would inprove, did not. Then got new stock injectors from LDS and still didnt improve. Replaced the fuel pressure regulator and also put in a race plug. I also blow air through all low pressure lines and dont feel like I have any restriction. With my experience working with high pressure hydraulics and air, I would imagine if my cp3 was bad I wouldn't be able to build up that much pressure. Any recommendations on what else to check or special test to run?
Nick821 is offline  
post #6 of 9 (permalink) Old 01-24-2020, 05:23 PM
Senior Member
 
denarli6.6's Avatar
 
Join Date: May 2018
Posts: 638
How many miles are on these trucks?

2016 LML Denali 2500
Mcgaughy's 2" drop shackle
Bilstein 5100
22x10 American Force Flux black w machined or Toyos on OEM wheels. Depends on the day of the week
Wehrli S300 kit w/ 66mm SXE
Wehrli CP3 conversion 10mm stroker
Profab Manifold & Up-pipes
Stock Trans For Now
Stock Sticks For Now
Air Dog 165 4G
denarli6.6 is offline  
post #7 of 9 (permalink) Old 01-24-2020, 07:21 PM
 
Join Date: Jan 2020
Posts: 3
On mine 310,000.
Nick821 is offline  
post #8 of 9 (permalink) Old 01-24-2020, 07:33 PM
LHN...We ARE the Joneses
 
Hook'em_Horns!'s Avatar
 
Join Date: May 2008
Location: Awww-stin, TX
Posts: 25,936
Send a message via Yahoo to Hook'em_Horns! Send a message via Skype™ to Hook'em_Horns!
Quote:
First noticed it when I put an edge insight on it,
You had a no power condition, then you installed the monitor and saw no rail pressure?

Or you have a problem with no power after you installed the monitor?

Or the truck runs fine and the monitor is showing false data?

2007 LBZ 3500 LT3 DRW Crew Cab, Sulastics, Putnam XDR 15K, B&W 30K-Turnover GN+Companion, Ride-Rite Air...EFI'd by Rob
2008 LMM 3500WT DRW Crew Cab, 8 'Flat/GN, Workforce Alum Toolbox, Ride-Rite Air

Use-ta Haves 2006-6.0 3500 WT DRW ExCab Flatbed, 2005-LLY 3500 LS DRW Crew Cab, 2002-LB7 3500 LS DRW Crew Cab
I Live my life in such a way that when my feet hit the floor in the morning...Satan shudders & says "Oh shit, he's awake!"
Hook'em_Horns! is online now  
post #9 of 9 (permalink) Old 01-24-2020, 08:10 PM
 
Join Date: Jan 2020
Posts: 3
Truck ran fine didnt really notice any power loss. I just bought the edge because I just wanted something to monitor everything with.
Nick821 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevy and GMC Duramax Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome