WOT rail pressure issue. Please help

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OBXdieselAddict

New member
So I'm at a bit confused, any help would be greatly appreciated.

I loose rail and fuel pressure at wide open throttle or during a heavy load. If I ease into tune 1, or 2 it pulls hard to about 24,000 and seems to hold ok but anything higher it drops and falls on its face.

Fuel setup:
*65% over SAC injectors
*Brand new hard lines, 1/2" fuel line, 1/2" CP3 fitting
*CP3(stock LB7 with about 10k on it)
*AirdogII 165 4G
*Sumped Titan tank

Rob Coddens with ATP has tuned the truck for the 65's as well

At first I thought I must have had some trash in the tank but when pulling the feed line off the back of the lift pump it pours out like a garden hose. A buddy of mine mentioned there is a fuel pressure relief valve of some sort on LB7's and that could be the issue. I no you can also block the rail return off with a Race valve? Could that be my issue?

Hopefully someone has been down this road and can help a brutha out.

Like always thanks for all the help guys.
 
Edit: My dumbass didn't see the titan tank after posting this :doh: You may still want to try to see if you get decent fuel flow. From the pump into a can or a bottle test from the return off the refief valve.


The relief valve is on a distribution block in the valley on LB7's they were not really much trouble on these motors. Also in the tank they had a pretty small draw straw and pickup that was a little restrictive. Maybe try seeing if you get good fuel floor from the Airdog into a bucket or gas can. The pickup in the tank could have some chit on it plus since the air dog always sends fuel back to the tank the extra flow could be working that pickup in the tank pretty good. Did the kit come with a new pickup or anything or just hook to the stock hose from the tank?
 
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rcr1978 said:
Edit: My dumbass didn't see the titan tank after posting this :doh: You may still want to try to see if you get decent fuel flow. From the pump into a can or a bottle test from the return off the refief valve.


The relief valve is on a distribution block in the valley on LB7's they were not really much trouble on these motors. Also in the tank they had a pretty small draw straw and pickup that was a little restrictive. Maybe try seeing if you get good fuel floor from the Airdog into a bucket or gas can. The pickup in the tank could have some chit on it plus since the air dog always sends fuel back to the tank the extra flow could be working that pickup in the tank pretty good. Did the kit come with a new pickup or anything or just hook to the stock hose from the tank?
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Maybe the draw straw is the issue then. The sump did not come with a straw so its just the stock straw setup if it didn't come with an aftermarket one with the Titan. I'm not sure. The truck actually had the titan when I bought it. I never had any issues with the old setup but then again pretty much everything on the whole fuel system is was replaced at the same time so now its hard to trouble shoot. I guess my best bet would be bucket or bottle testing to see where my restriction or blockage are? Do people normally go with the "race valve" setup or block off on LB7's? I had always heard it wasn't really needed.
 
I was thinking looking at your top post you have a actual sump like this

http://store.fassride.com/detail/accessories/fuel-sump-kits/diesel-fuel-sump-bowl-only.php

If not yes definitely check the pickup/draw straw in the tank, normally people do not use the race valve for LB7's unless maybe your trying to run over 180mpa rail pressure but I've personally never had any trouble with any of them like LLY up ones and I ran 175MPA on my old tunes before the motor let go still without popping the valve. Test it first and see then you would know.
 
Have you sent a log file to Rob?

As mentioned, the lb7 rarely had issues with the relief valve. You can check the return off that if you think it's blowing open during high pressure.

Does the rail pressure increase over 24k on the bigger tunes before it drops off? Or do the bigger tunes just not hold rail pressure at all? A stock pump is going to be very limited on pulse width with those 65% overs.
 
JWhite said:
Have you sent a log file to Rob?

As mentioned, the lb7 rarely had issues with the relief valve. You can check the return off that if you think it's blowing open during high pressure.

Does the rail pressure increase over 24k on the bigger tunes before it drops off? Or do the bigger tunes just not hold rail pressure at all? A stock pump is going to be very limited on pulse width with those 65% overs.
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I haven't, I really need too. I have an autocal but I have a mac laptop. I need to buy a cheap laptop that I can download efi on. I'm just kinda taking shots in the dark without sending logs.

none of the tunes will go above 24k, its not a slow drop either when it decides to fall it just looses pressure all together. I ordered the race valve so I'll try throwing that in this weekend.

My carrier bearing on my 2 piece drive shaft decided it didn't want to carry on with life so I'm dealing with that this weekend also. I pulled the drive shaft but now I'm kinda thinking I should go with a 1 piece. I need to measure tonight to see what size I need though. Talked to Dirty Hooker today about getting a used 1 piece from them but I need to find out my measurements.
 
rcr1978 said:
I was thinking looking at your top post you have a actual sump like this

http://store.fassride.com/detail/accessories/fuel-sump-kits/diesel-fuel-sump-bowl-only.php

If not yes definitely check the pickup/draw straw in the tank, normally people do not use the race valve for LB7's unless maybe your trying to run over 180mpa rail pressure but I've personally never had any trouble with any of them like LLY up ones and I ran 175MPA on my old tunes before the motor let go still without popping the valve. Test it first and see then you would know.
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Yes, that's the exact sump I have. No draw straw upgrade.

I was looking at them last night. The fass draw straw setup is a bit pricey. I found the airdog setup for 50-60 I might go with that.
 
If you have that sump there is no draw straw or one needed, I really doubt there is a supply issue to the pump unless there's something in the hose or sump.
 
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rcr1978 said:
If you have that sump there is no draw straw or one needed, I really doubt there is a supply issue to the pump unless there's something in the hose or sump.
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It seems to be supplying to the lift pump pretty well. I pulled the 1/2 feed line that goes into the sump from the tank and it was coming out like a garden hose. One night this week When I get a little time I'll get that race valve put on to see if that helps. hopefully that solves my issue. I will post when I get a chance.
 
Got my race valve in so I'll try to get it in the truck in the next few days. works been crazy this week.

Also hooked the autocal up I had thrown a P0087 low fuel rail pressure.

Really hoping this PPE replacement fuel pressure relief valve does the trick. Really not sure what else it could be after that unless I just have a faulty CP3
 
I guess I just don't expect the stock pump to carry anything with those bigger injectors. I think you're just asking to much of the pump.
 
BRE said:
I guess I just don't expect the stock pump to carry anything with those bigger injectors. I think you're just asking to much of the pump.
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The stock pump definitely is my bottle neck. I know there is no way it will support anything past 600-650hp or so. I kind of wanted to stick with the stock pump as long as possible though to keep it as a fail safe for my bottom end. Wont be for a few years I'll be able to get a bottom built.

I still shouldn't be loosing rail pressure like I am though. Really hoping the rail plug will solve my issue, I mean I know LB7's don't normally have an issue with it but then again I've got 270k miles so the spring might just not be holding anymore.

I will know better Saturday when I have a chance to put it in the truck. Hopefully my drive shaft gets here before then so I will be able to take it down the road.
 
Kind of living in a fantasy world if you think that stock pump is going to allow you to do much of anything with those injectors.

Stock LB7/LLY pump is only going to do 24k-ish rail pressure. The fact that tune 1 and 2 hold rail only supports that you need way more pump for those injectors.
 
Phooker said:
Kind of living in a fantasy world if you think that stock pump is going to allow you to do much of anything with those injectors.

Stock LB7/LLY pump is only going to do 24k-ish rail pressure. The fact that tune 1 and 2 hold rail only supports that you need way more pump for those injectors.
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Yea I know, I really need to dual it. Not in the budget at the moment though lol

A nice new Industrial shinny looking wheel would look nice in there though lol
 
OBXdieselAddict said:
Yea I know, I really need to dual it. Not in the budget at the moment though lol

A nice new Industrial shinny looking wheel would look nice in there though lol
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10mm pump would have a better chance and is several hundred cheaper than dual pumps.

LBZ regulator and retune might net a little bit more power, but not much.
 
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