Low fuel rail pressure shimmed and lift pump

[Chadf212]

So guys what's next did the bottle test already have a shimmed valve and a fass deleted the whole stock filter assembly. It won't throw a low fuel rail code until
100ish in my big maxx effort tune. But it's deffinitly defueling before that it asks for 28 on dfrp I believe and it's only Getting to about 24 25 on actual frp. And at idle the frp kinda bounces around from like a high of 5.2 and a low of 4.7. Could
It be the cp3 fuel pressure regulator? Truck has 123,000 on it. Thanks for any suggestions on what to test next

 

[JoshH]

What pulse width?

 

[Chevy1925]

actual is 24-25k and its throwing a code? you sure its not 14-15k actual when the code is occuring?

 

[mike diesel]

Are you sure it is actually making it to 24,000-25,000 psi? Those are still good numbers, and from my experience I haven't seen a truck throw a low rail pressure code only dropping 3000 psi.

 

[mike diesel]

actual is 24-25k and its throwing a code? you sure its not 14-15k actual when the code is occuring?

Tree'd

 

[Chadf212]

Ok my bad I'm off here ya the last time I watched the gauges was at the strip where it won't actually throw the code and it runs 22 and asks for 26 I haven't thrown the code lately cause I haven't had a chance to. But I'll go do it here shortly I'm sure it's much lower when it throws the code sorry for the confusion.

 

[mike diesel]

If you can log it too that would help.

 

[JoshH]

I believe it has to be 22 mPa below desired for a set amount of time, but I'm not sure what the time is. I'm going to guess 10 seconds since that's what it uses for several other things like boost and MAF.

Edit: looked it up on alldata. Here's what they say.

CONDITIONS FOR SETTING THE DTC

P0087
The actual FRP is more than 15 MPa (2,176 psi) below the desired FRP.OR
The actual FRP is less than 22.5 MPa (3,263 psi) .

 

[Chadf212]

No I wish I could log it. My local diesel shop did my efi.

 

[JoshH]

Where are you? Have you talked to the shop that did the tunes for you?

 

[Chadf212]

Ok check this video out I just took of my cts http://youtu.be/6mX0F8pTgSo it spikes at 29 then drops to 15 lol wtf

 

[Chadf212]

Ya I did they want to check injectors or replace the cp3 I just dropped 5k on a trans so I just kinda want to fix it myself you know I'm in Northern California

 

[JoshH]

Since you didn't stay on the screen I couldn't tell for sure, but that looks like a FPRV blowing open.

 

[Chadf212]

It's tricky recording at 100 but why am I so far below dfrp the whole time? I guess I'll bottle test again I have three shims in the sucker.

 

[JoshH]

I just rewatched your video on my computer where I could see it better. Is that desired rail pressure displayed in the lower left corner of the screen? If so, desired is falling off, that's why your rail pressure drops to 15 mPa. I don't think it is opening the valve. You need to talk to your tuner about your issues. I'm not going to ask for a bunch of info on someone else's tune or tell them how to write them.

 

[Chadf212]

Ok ya it is the disired. Ok I will is my cp3 just not strong enough? Is there any way to test the cp3?

 

[L0B6Z]

I see you have ported fittings. I have the same issue ever since I did ported fittings. My rp drops to 21000 at wot sled pulling. I can also get it on the street in my race tune if I launch it and ride 4th out to 3500 rpm. I'm gonna find a stock fitting and put it back in and try it.

 

[Hot COCOAL]

Unless you guys are running a stroker pump or duals, you should only have a ported fitting in the drivers side rail...I made that mistake. So if you're running a stock CP3 and dual ported fittings, putting a stock rail fitting in the pass side rail "should" help, providing there's no underlying issues at play

 

[plowboy_lbz]

I fought low rp for a long time. The shop that tuned it wanted to replace the injectors and cp3. Added a modified pump, didn't fix it. Turned out to be their shitty tuning. I see rob tuned yours so that is good. But he might be asking for a little more than your cp3 can handle. Have you tried contacting ATP?

 

[L0B6Z]

Unless you guys are running a stroker pump or duals, you should only have a ported fitting in the drivers side rail...I made that mistake. So if you're running a stock CP3 and dual ported fittings, putting a stock rail fitting in the pass side rail "should" help, providing there's no underlying issues at play

I only have drivers side ported. Don't know about iirc. But I agree.. I keep beeing told u don't need to touch em at all