Rail pressure is 24k at idle

O

Oliver77

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May 19, 2010
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My sisters boyfriends truck is running at 24k rail pressure at idle. He has ats dual cp3's that he has had on there for about three months without an issue. Does anyone have a clue on where to start we have checked all plugs and all that. Any help would be appreciated. His lp pressure is running about 20psi but has been since we installed the duals.
 
Take the belt off so the top pump won't run unhook the controller and just run the factory cp3. I bet it runs fine then, probably the controller.
 
I got a buddy that will let me borrow a controller to try tomorrow. We will stick it on there to eliminate the controller. Also read you can take the fca off and shake it, if it rattles it's still good. I will give an update tomorrow.
 
could be totally unrelated, but i had high rail pressure just off idle for a while. ended up being the Air Temp/press sensor at the air filter.
 
I had high rail pressure at idle and it was the fca pig tail. The pig tail looked to be in perfect condition also
 
Thanks for the input guys. We are going to change the controller and harness today and pull the fca off and check it.
 
Ok guys we took the belt off and hooked up the bottom cp3 and it runs fine. So I went and got my buddies controller off his truck and put it on there and still have the same problem max rail pressure at idle. Does anyone have any suggestions to what it could be? Maybe the fca on the top pump. Also lowered lp pressure to 15psi.
 
Word to the wise, don't change things during troubleshooting that you don't have to.
Swap fca's on the pumps. Should be obvious where the failure lies then.

Squeaky Wheel
 
So you are saying to swap the top fca with the bottom one and take the belt off to see if it is that fca correct?
 
TX_5.9 said:
Try a known good FCA up top to rule it out.

sent from my kookie phone
Click to expand...

I would, but I don't have one laying around that it have access too. I will update on what we find out after swapping fca's in a little while.
 
Well pulled the top fca and shook it, it rattles and ohms to 2.9 ohms. According to my readings that means it's good. What do you guys think?
 
Ok it's good when when you swap fca's and remove the belt. That rules out the fca's being the problem. So we checked the voltage off of the original controller and it has no voltage. Put the ppe controller back on that I borrowed and it is showing 12 volts at the plug for fca. So I'm pretty sure it's the ats controller bad and the ppe controller had too much lp pressure causing it to raise the voltage to high and causes the rail pressure to max out. Does that make since?
 
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So I drove my truck last night and no issues. Today before I started the truck I installed some led lights in doing so I disconnect the batteries grounds (dual cp3 controller ground is on battery ground terminal). Got done with the install and went to fire it up to back it out of garage and rail pressure is 25k+ on my gauge. So now I'm like WTF happened since last night. I double checked the grounds and all is good. Going to check the FCA on the top pump tomorrow. Hopefully it's not the controller.
 
Did you guys ever figure out the problem? I am having a similar problem with my '03. Changed controller and rail pressure sensor and it maxes out rail pressure with the belt unhooked and the controller unplugged to top pump. FCA swap is my next trial.
 
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