Advertisement
If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Home Who's Online Today's Posts HP Calculator CompD Gift Shop Mark Forums Read
Go Back   Competition Diesel.Com - Bringing The BEST Together > Tech Area- Dodge > Dodge Tech > 03-07 3rd Gen.
Register Members List Timeslips EFI Live Library Invite Your Friends FAQ Calendar Mark Forums Read

Closed Thread
 
Thread Tools
Old 06-10-2019, 05:27 PM   #1
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Teach me about rail pressure

Mechanic, but gasser...not diesel smart.

Issue: Ive been trying to hunt down an intermittently stuck open injector. Today I spent a couple hours disabling each injector and going for a ride around an empty parking lot.

Surprisingly it didn't matter which injector was unplugged, it would just stick open and roll black smoke and essentially stall and have no power (was still running, but no power and still blowing smoke).

I started looking at rail pressures. I sit at 7700-8000 rail pressure at idle, which I've been told is a bit too high...I need 5500-6000 at idle I've been told.

When the motor smokes out and dies, I sit around 11-12,000 rail pressure at a dead stop idle. If I try to give it has, it will bump to 14-15,000 but the truck won't respond at all...won't have power, will smoke a little more and that's all.

So I don't think I have an injector problem, but a problem causing high rail pressure (which I was told could stick an injector at idle).


So how does the rail pressure build/release?

Obviously the cp3 builds the pressure that gets sent to the rail. I'm assuming there's a regulator or relief valve somewhere on the rail?

I know there's the FCA that is ecm controlled that is on the back of the cp3...is this also the overflow/relief valve?

What would cause high pressure at idle, and cause rail pressure to stick?


Obd 2 isn't working right now, in the process of dealing with that too.

Sent from my Moto Z (2) using Tapatalk
 
Old 06-10-2019, 05:36 PM   #2
ramthiscummins

Name: ramthiscummins
Title: Too Much Time
Status: Not Here
Join Date: Sep 2010
Location: Canada EH!
Member`s Gallery
Posts: 589
There is a prv which you can check to see if it is working,

I would check the feed tubes first though (since that is free and relatively easy).
__________________
2003 QCSB cummins, DDP 12mm CP3, DDP SM 150% overs, a turbo, Firepunk diesel 48re
 
Old 06-10-2019, 05:42 PM   #3
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by ramthiscummins View Post
There is a prv which you can check to see if it is working,

I would check the feed tubes first though (since that is free and relatively easy).
What do I need to check on them?

Engine was just rebuilt, with brand new bosch injectors AND feed tubes. I torqued them exactly to spec according to the book. Was looking today and my torque wrench may have been a little under torque (I used it on something else today).
 
Old 06-10-2019, 05:44 PM   #4
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by ramthiscummins View Post
There is a prv which you can check to see if it is working,

I would check the feed tubes first though (since that is free and relatively easy).
Where is the pressure relief valve and how does it function? If its just functions mechanically, then I would assume it would only relieve maximum pressure, which I dont think is an issue for me since it doesn't get stuck at max, its getting stuck at 11-12kish
 
Old 06-10-2019, 06:00 PM   #5
Mark Nixon
 
Mark Nixon's Avatar

Name: Mark Nixon
Title: No Savior among the flesh
Status: Not Here
Join Date: Feb 2009
Location: Brownville, Nebraska
Member`s Gallery
Posts: 8,676
Quote:
Originally Posted by Hoiyay View Post
Where is the pressure relief valve and how does it function? If its just functions mechanically, then I would assume it would only relieve maximum pressure, which I dont think is an issue for me since it doesn't get stuck at max, its getting stuck at 11-12kish
It's on the rail, under the return line, next to the rail sensor.
It's mechanical.

Mark.
__________________
If you or I did business like the PEOPLE in government do business, we'd be put in jail. Government is coercive.
Anarchy: The state of existence where there are no masters & no slaves. Therefore, Anarchy means the ABSENCE OF SLAVERY, or, in other words, FREEDOM.
 
Old 06-10-2019, 06:02 PM   #6
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by Mark Nixon View Post
It's on the rail, under the return line, next to the rail sensor.

It's mechanical.



Mark.
Does it only work for maximum pressure then? How would it know to fluctuate pressure?

Sent from my Moto Z (2) using Tapatalk
 
Old 06-10-2019, 07:23 PM   #7
JWhite
 
JWhite's Avatar

Name: JWhite
Title: Trained monkey
Status: Not Here
Join Date: Aug 2009
Location: F Burg Ohio
Member`s Gallery
Posts: 1,817
12kpsi won't stick an injector at idle. Best bet is to come up with a plug to remove one injector feed line at a time
__________________
GMC with a LiLLY
 
Old 06-10-2019, 07:32 PM   #8
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by JWhite View Post
12kpsi won't stick an injector at idle. Best bet is to come up with a plug to remove one injector feed line at a time
That's what I've done though. It seems as if it's an electrical issue. Runs good down the road, come to a stop and it does it sometimes. Turn truck off, turn back on 5 seconds later and it's cleared out.

Did it with ever injector disconnected.


Sent from my Moto Z (2) using Tapatalk
 
Old 06-10-2019, 08:21 PM   #9
xDiesel03
 
xDiesel03's Avatar

Name: xDiesel03
Title: Diesel Enthusiast
Status: Not Here
Join Date: Oct 2013
Member`s Gallery
Posts: 225
Could also be your fuel rail pressure sensor. I chased an issue for quite a while that ended up being a bad pigtail leading into the sensor plus the actual sensor. Backprobe the sensor and see what you have for voltage. Do you have the ability to monitor commanded vs. actual fuel rail pressure? Mine was intermittent and then got stuck at 17k psi.
__________________
2003 2500 QCSB 4x4 3.73 - Firepunk HPT Tuned, BBI Stage 2's, DAP 63/68/12, Hamilton [624/1050 and 680/1206 with Water/Meth]

2012 2500 CCSB 4x4 3.73 Firepunk EFI and Comp3, D&J Built 6.7L, S&S 200%, ATS Dual CP3 w/ Exergy 12mm, S366/S483 Compounds [1086/2289]
 
Old 06-10-2019, 08:58 PM   #10
Tobin
 
Tobin's Avatar

Name: Tobin
Title: 5.7 IDI Powaa!
Status: Not Here
Join Date: Oct 2008
Location: Oviedo, FL
Member`s Gallery
Posts: 1,496
Quote:
Originally Posted by Hoiyay View Post
That's what I've done though. It seems as if it's an electrical issue. Runs good down the road, come to a stop and it does it sometimes. Turn truck off, turn back on 5 seconds later and it's cleared out.

Did it with ever injector disconnected.


Sent from my Moto Z (2) using Tapatalk
Are you electrically disconnecting the injectors or removing the fuel line and capping the rail?
__________________
2006 Dodge 2500 QCLB 4x4 Goerend 48RE

1977 F250 RCLB 4x4 "High Boy" 12 valve, 180 pump, 5x.014, S363/S475, Goerend 47RH, NP271, 2007 D60/Sterling 10.5, 40" Toyo MTs
 
Old 06-10-2019, 09:05 PM   #11
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by Tobin View Post
Are you electrically disconnecting the injectors or removing the fuel line and capping the rail?
Right now just electrically. Since it's not just stuck open I'm just disconnecting it electronically.

It's either not working, or wide fking open it seems. I dont see how capping off the fuel rail would prevent fuel from getting in cylinder since it's not leaking. But I'm here to learn.

Sent from my Moto Z (2) using Tapatalk
 
Old 06-10-2019, 09:06 PM   #12
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by xDiesel03 View Post
Could also be your fuel rail pressure sensor. I chased an issue for quite a while that ended up being a bad pigtail leading into the sensor plus the actual sensor. Backprobe the sensor and see what you have for voltage. Do you have the ability to monitor commanded vs. actual fuel rail pressure? Mine was intermittent and then got stuck at 17k psi.
I don't have a tuner and obd2 is dead for now.

I could back probe somewhere, but I wouldn't know how to interpret the volts into "asked for" rail pressure

Sent from my Moto Z (2) using Tapatalk
 
Old 06-10-2019, 10:48 PM   #13
JWhite
 
JWhite's Avatar

Name: JWhite
Title: Trained monkey
Status: Not Here
Join Date: Aug 2009
Location: F Burg Ohio
Member`s Gallery
Posts: 1,817
Quote:
Originally Posted by Hoiyay View Post
That's what I've done though. It seems as if it's an electrical issue. Runs good down the road, come to a stop and it does it sometimes. Turn truck off, turn back on 5 seconds later and it's cleared out.

Did it with ever injector disconnected.


Sent from my Moto Z (2) using Tapatalk
Quote:
Originally Posted by Hoiyay View Post
Right now just electrically. Since it's not just stuck open I'm just disconnecting it electronically.

It's either not working, or wide fking open it seems. I dont see how capping off the fuel rail would prevent fuel from getting in cylinder since it's not leaking. But I'm here to learn.

Sent from my Moto Z (2) using Tapatalk
You need to cap off the rail to isolate the injector from pressure. This 100% proves whether it's the culprit.

And on the rail pressure sensor, it's 0-5v with .5v being zero and 4.5v being max (so probably around 26k)
__________________
GMC with a LiLLY
 
Old 06-10-2019, 10:53 PM   #14
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by JWhite View Post
You need to cap off the rail to isolate the injector from pressure. This 100% proves whether it's the culprit.



And on the rail pressure sensor, it's 0-5v with .5v being zero and 4.5v being max (so probably around 26k)
I can cap off the rail. But educate me how that would make a difference please. If injector is "dead"...unplugged, it's shut closed. Why would it matter if it's got pressure behind it? I can see if it was just leaking a little, but this is dumping.

Got it on rail pressure! Thanks.

Where should I measured for what the ecm is asking for? At the fca?

Sent from my Moto Z (2) using Tapatalk
 
Old 06-11-2019, 10:05 PM   #15
JWhite
 
JWhite's Avatar

Name: JWhite
Title: Trained monkey
Status: Not Here
Join Date: Aug 2009
Location: F Burg Ohio
Member`s Gallery
Posts: 1,817
Quote:
Originally Posted by Hoiyay View Post
I can cap off the rail. But educate me how that would make a difference please. If injector is "dead"...unplugged, it's shut closed. Why would it matter if it's got pressure behind it? I can see if it was just leaking a little, but this is dumping.

Got it on rail pressure! Thanks.

Where should I measured for what the ecm is asking for? At the fca?

Sent from my Moto Z (2) using Tapatalk
If everything works like it should, you'd be right. But the part that actually seals the fuel while the solenoid is de energized might be problematic.

You'd be best to watch desired pressure on a scanner, not any straight forward way to measure that with a volt meter on the engine.
__________________
GMC with a LiLLY
 
Old 06-12-2019, 02:44 PM   #16
Hoiyay

Name: Hoiyay
Title: Green Behind the Ears
Status: Not Here
Join Date: Dec 2018
Member`s Gallery
Posts: 74
Quote:
Originally Posted by JWhite View Post
If everything works like it should, you'd be right. But the part that actually seals the fuel while the solenoid is de energized might be problematic.



You'd be best to watch desired pressure on a scanner, not any straight forward way to measure that with a volt meter on the engine.
Got it.

Injectordirect already gave me an RMA for the injectors. Going to send in and have them tested since I have to wait on my cluster to get here anyways. Hopefully that fixes the obd2.

I replaced fca and rail pressure sensor...one at a time. Not a single change.

When changing out rail sensor....I noticed bubbles in there. Not sure If it from opening rail pressure or making them.

Checked all over, no leaks. Even at high idle.

Sent from my Moto Z (2) using Tapatalk
 
Old 06-12-2019, 03:20 PM   #17
biggy238
 
biggy238's Avatar

Name: biggy238
Title: Too Much Time
Status: Not Here
Join Date: Aug 2008
Location: Just North of Wrong
Member`s Gallery
Posts: 10,820
Isolating the injector by capping the rail removes its pressure source so that no fuel can access it.
Isolating it electrically only eliminates the solenoid and armature, but does not disable the valving inside the injector.
Generally speaking, the armature on an injector isn't powerful enough to meter the fuel directly when at operating pressure. The solution is to use pilot operation, a smaller quantity of fuel at lower pressure, in order to shift the pintle open. This action is what actually meters the fuel used for combustion.
An injector can malfunction mechanically and still meter fuel when it isn't being electrified. Isolating the suspect injector is the only way to be certain it isn't metering.



Sent from my SM-G950U using Tapatalk
__________________
Check out @bdmaximusworx

05.5 Campanella White TDi Jetta 5spd 45.5MPG
-Little Sexy
'10 Silver F250 CCLB 4X4 6.4L cummins Swapped
Insta @trash.panda250
 
Old 06-12-2019, 03:21 PM   #18
biggy238
 
biggy238's Avatar

Name: biggy238
Title: Too Much Time
Status: Not Here
Join Date: Aug 2008
Location: Just North of Wrong
Member`s Gallery
Posts: 10,820
Diesel Common Rail Injection Facts 1 - YouTube

Sent from my SM-G950U using Tapatalk
__________________
Check out @bdmaximusworx

05.5 Campanella White TDi Jetta 5spd 45.5MPG
-Little Sexy
'10 Silver F250 CCLB 4X4 6.4L cummins Swapped
Insta @trash.panda250
 
Old 06-15-2019, 01:36 PM   #19
ramthiscummins

Name: ramthiscummins
Title: Too Much Time
Status: Not Here
Join Date: Sep 2010
Location: Canada EH!
Member`s Gallery
Posts: 589
Not sure if this was mentioned but do you have a rail pressure gauge?
I would not recommend getting one as they can mess up the wiring if not done correctly. If you have one check the wires and check the connections at the rail.
__________________
2003 QCSB cummins, DDP 12mm CP3, DDP SM 150% overs, a turbo, Firepunk diesel 48re
 
Old 06-27-2019, 12:44 AM   #20
SixOhh
 
SixOhh's Avatar

Name: SixOhh
Title: EPA unfriendly
Status: Not Here
Join Date: Aug 2008
Location: Magnolia, TX
Member`s Gallery
Posts: 1,108
Quote:
Originally Posted by Hoiyay View Post
What do I need to check on them?

Engine was just rebuilt, with brand new bosch injectors AND feed tubes. I torqued them exactly to spec according to the book. Was looking today and my torque wrench may have been a little under torque (I used it on something else today).

so you are saying you leave your toque wrench torqued up after use?
__________________
07' Silver 2500 5.9 4x4 LWB
Goerend 48re-csp5/EFI- T&C Mild Cp3-F1 Apex 7.5 -S369sxe Amsoil
Coolant Bypass -Airdog-D&J- Hamilton 188/220 -AFE-ARP Opti-Lube
H-Town Off-Road
 
Closed Thread

Thread Tools

Posting Rules
You may not post new threads
You may not 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

Forum Jump


All times are GMT -5. The time now is 11:08 AM.

 


Powered by vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2006 - 2024, CompetitionDiesel.com
all information found on this site is property of www.competitiondiesel.com