What is the lowest rail pressure you can run with out problems?

[J.Davy]

How low can it go without feeling it surge or miss?I am starting to have a fueling problem and it surges and is losing power on the top end. The rail is dropping to 9000 psi while it is requesting 23000+. This problem started about 2 weeks ago and only happens when stacking both boxes.

 

[Vaughn MacKenzie]

Sounds like you're sucking the rail dry. . . time for a modded CP3?

 

[J.Davy]

I will get it modified but I want to make sure that is the problem as it seems to have developed within the last few weeks. If the pump is going weak will they fix that problem as well?

 

[sag2]

Either you are overflowing what the lift pump can handle, or you have a leak on the high pressure side that is maxing out the lift pump. If you continue to drive it like that you will ruin the CP3 from fuel starvation. If you started to cause the problem from stacking the boxes, why would DC pay for it? The stock lift pump is not designed to to handle the extra demands placed on it from the boxes, especially if you are blowing fuel off the pop off valve.

 

[J.Davy]

sag2,who said anything about D. C. paying for it?The weak pump I was hoping to get fixed was the cp3,meaning i hope they do more then just drill out a few passages or whatever,I was hoping they go right through the whole pump when they modify it and determine why it was getting weak in the first place fix it as well as make it better. I have a 150 gph F. A. S. S. on it. My inlet pressure never goes below 11 psi. I am hoping it is something simple.

 

[JVolpe]

I was talking with Mark at TST on the phone about PowerMaxCR Twins program and stacks, he commented about seeing the same thing while they were testing. If I remember right he stated the exact same PSI readings, asking for 23,000 and getting 9,000. Seems to be a few working on modded CP3s. Please let us know if you go that route and the results.

 

[MikeS1]

Before my cp3 mods with my tst stacked with the EZ; tst on 9x9 (twins program)and EZ on 4 I could pull my rail pressure down to 12k and it would really fall on its face. Maybe check for some restriction on where it plugs into the cp3, where are you reading your fuel pressure from? Mike

 

[JStieger]

Before my cp3 mods with my tst stacked with the EZ; tst on 9x9 (twins program)and EZ on 4 I could pull my rail pressure down to 12k and it would really fall on its face. Maybe check for some restriction on where it plugs into the cp3, where are you reading your fuel pressure from? Mike

I read somewhere on this site (or the other site) about someone dynoing while monitoring rail pressure and found whatever #x# TST setting that gave the most power equated to keeping the rail pressure > the same 12,000-13,000 psi.

 

[J.Davy]

Mike,my pressure is read at the cp3 inlet. What are your high pressure readings after the cp3 mod?When your pressure was down around 12000 did you feel the truck hesitate?

 

[MikeS1]

Mike,my pressure is read at the cp3 inlet. What are your high pressure readings after the cp3 mod?When your pressure was down around 12000 did you feel the truck hesitate?

I am also checking my fuel pressure at the cp3, but at 12k the truck just fell on its face and I believe that my TST was on 7 when this happend. I have only had this modification for less than a month and have not had time to hook it back up to a scan tool but there is a noticeable difference in power, plus I can run my TST up to 9 Ramifier full on and still break the 600hp mark now where before I did not even break 500, so I would say that the cp3 mods work well. Mike

 

[MikeS1]

I am also checking my fuel pressure at the cp3, but at 12k the truck just fell on its face and I believe that my TST was on 7 when this happend. I have only had this modification for less than a month and have not had time to hook it back up to a scan tool but there is a noticeable difference in power, plus I can run my TST up to 9 Ramifier full on and still break the 600hp mark now where before I did not even break 500, so I would say that the cp3 mods work well. Mike

Sorry my TST was on 9 I hit the wrong button... .

 

[J.Davy]

Ok thanks Mike. I am leaning towards my rail relief valve more and more as today I was looking at it and there is a film of dirt around the banjo head fitting and I am thinking it might have poped at some point.

 

[TCluff]

Ok thanks Mike. I am leaning towards my rail relief valve more and more as today I was looking at it and there is a film of dirt around the banjo head fitting and I am thinking it might have poped at some point.

my rail pressure hit 9000 psi at bully dog and the truck also just fell on its face, same problems, never gets below 11 or 12 psi at the inlet of the cp3, i couldnt run the tst twins program over 4x3 with the ts at 50% or 100%, the rail pressure is gone as soon as the twins light, i too replaced the rail relief valve 420. 00 from cummins intermountain, with no noticeable change in power, before you spend the money, borrow a buddys

 

[J.Davy]

TCluff,what do mean fell flat on it's face?Does it lose a bunch of power and go into limp mode?

 

[TCluff]

TCluff,what do mean fell flat on it's face?Does it lose a bunch of power and go into limp mode?

it feels like you are backing out of the throttle and at 2800 and above rpm it has a slight surge feel :{

 

[JStieger]

it feels like you are backing out of the throttle and at 2800 and above rpm it has a slight surge feel :{

Did you get your rail pressure problems sorted out that you had at Dog Days?

 

[TCluff]

Did you get your rail pressure problems sorted out that you had at Dog Days?

i have ideas, and a place to have my cp3 worked, i also want the same injectors you have, how are the new ones Oo.

 

[JStieger]

i have ideas, and a place to have my cp3 worked, i also want the same injectors you have, how are the new ones Oo.

I only have about 1,000 miles on them, but so far I like them. They are a lot less smokier than the DD3's I had before, even before the SPS 66 turbo. With the SPS 66 turbo the smoke clears up pretty quick, but I think my clutch is starting to slip with J/A on 5. Like the DD3, the 3-flows are really smoooooth power that follows the factory HP/Torque curves.



I towed my jeep back from Crescent Valley this afternoon with the J/A on 2 (~405 HP based on previous DD3/Juice dynos I did) and the truck only smoked black on initial take off or accelleration then quickly cleared up. Once I get some free time I hope to go back to Meridian Motorsports the next few weeks or so and redyno the injector J/A combo because it does feel stronger based on my clutch slipping now versus not slipping before.



Next time I see you around town we'll have to chat. This is what I towed this afternoon so you'll probably see me around town driving it while the weather is good. Don't get any smoking ideas since I don't have a top or doors for it :-laf !



BTW, back to the rail pressure topic, I picked up a SPA rail pressure gauge, but still have to mount it. It would be interesting to see what the injectors and J/A does because the 305/555 version of the Juice does rail pressure also, but only up to ~2100 rpms and I can definitely feel some power cutting out right around this rpm and then quickly come back on as if it is switching to another fueling map or something.

 

[jpgranieri]

I was in Canada last week and got a 'Check Engine Lite on'. Took it to the dealer in Swift Current wherein diagnostic revealed only 21 PSI on the fuel rail. (minimum is 870PSI). Mechanic decided it needed a new pressure rail sensor. However none was available and since the truck was not in the limp mode they decided it would be safe to drive it home. (Northern Calif. ) No problem was experienced except for smoke and low MPG. Local dealer here now has the truck and confirms problem and fix. but again no sensors are available. Dealer informs me that the 600 has been experiencing this problem.

Anybody on the forum confirm this problem??



JPG... already missing my 1995 dually. Now it's a 2005 Quad cab 4x4 SLT.

 

[BlackTxThunder]

Where can you get a modified cp3 besides ATS. They are the only ones I have spoken with about it. I have the same problem too I am almost positive.

I don't have the equipment to measure rail pressure or know exactly how to do it. But with TST -twins flash up like 7/7 and BullyDog on CL setting it does seem to fall off.