12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

Fuel Pressure Decreases with Throttle...

Old Mar 3, 2013 | 07:49 AM
  #1  
Sudia247's Avatar
Thread Starter
|
Diesel Enthusiast
Joined: Jun 2010
Posts: 272
Likes: 13
From: Sacramento, CA
Default Fuel Pressure Decreases with Throttle...

So I finally got my fuel pressure gauge all hooked up. It's an Isspro Ev2, and I also have the Tork Tek OFV020 Adjustable Overflow Valve. At idle, the gauge reads 25 psi, which is what Tork Tek states it should be. But as I give the engine some fuel, the fuel pressure decreases, instead of increasing.. I have not brought it to WOT yet, but bringing it up to just over 2k rpm, with about 10 PSI boost, the fuel pressure is about 20 psi...

My truck is all factory besides an Air Intake, and 4" Straight Pipe..
 
Reply
Old Mar 3, 2013 | 08:01 AM
  #2  
mysterync's Avatar
Diesel Bombers Sponsor
Joined: Mar 2007
Posts: 3,791
Likes: 367
From: Blowing Rock,NC
Default

How old is the fuel filter? Could be a failing lift pump. A cracked fuel heater will cause a similar complaint with a hard start. The in tank module can also be restricted!

Sent from my DROID RAZR using Tapatalk 2
 
Reply
Old Mar 3, 2013 | 09:00 AM
  #3  
sweetv8s10's Avatar
Diesel Enthusiast
Joined: Nov 2009
Posts: 498
Likes: 20
From: El Dorado Springs MO
Default

When it is under a load it will drop. 20 psi sounds ok to me.
 
Reply
Old Mar 3, 2013 | 09:17 AM
  #4  
mysterync's Avatar
Diesel Bombers Sponsor
Joined: Mar 2007
Posts: 3,791
Likes: 367
From: Blowing Rock,NC
Default

Originally Posted by sweetv8s10
When it is under a load it will drop. 20 psi sounds ok to me.
I guess i should have read closer. I saw 10 psi .

Sent from my DROID RAZR using Tapatalk 2
 
Reply
Old Mar 3, 2013 | 09:58 AM
  #5  
Sudia247's Avatar
Thread Starter
|
Diesel Enthusiast
Joined: Jun 2010
Posts: 272
Likes: 13
From: Sacramento, CA
Default

So it's normal to drop fuel pressure under load? But the fuel filter is new, about 2k miles on it. I removed the fuel heater as well.

I was thinking it could be a failing lift pump, but I wasn't sure, Ill give it WOT and see where it drops to or if it stays at 20 PSI..
 
Reply
Old Mar 3, 2013 | 10:54 AM
  #6  
mysterync's Avatar
Diesel Bombers Sponsor
Joined: Mar 2007
Posts: 3,791
Likes: 367
From: Blowing Rock,NC
Default

Originally Posted by Sudia247
So it's normal to drop fuel pressure under load? But the fuel filter is new, about 2k miles on it. I removed the fuel heater as well.

I was thinking it could be a failing lift pump, but I wasn't sure, Ill give it WOT and see where it drops to or if it stays at 20 PSI..
As engine rpm increases the lift pump produces more volume so it shouldn't drop much at all past 20. You could raise your baseline pressure up a bit more. If it drops when rpms are raised with no load then you should be looking for issues.

Sent from my DROID RAZR using Tapatalk 2
 
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Dbleo351
Chevy/GMC 6.2L and 6.5L
19
Nov 20, 2016 09:34 AM
ctjkelley
Chevy/GMC 6.2L and 6.5L
7
Jun 3, 2015 06:01 AM
RatsMC
Chevy/GMC 6.2L and 6.5L
19
May 4, 2015 05:25 PM
robbyS
5.9 Liter CR Dodge Cummins 03-07
3
Apr 16, 2015 02:22 PM
moneypitk5
Chevy/GMC 6.2L and 6.5L
3
Feb 12, 2015 11:01 AM


Thread Tools
Search this Thread

All times are GMT -5. The time now is 02:33 PM.