LLY: How much psi is to much for a lift pump

T

TRUBBS

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Got a stock fuel pump off a 7.3l I was thinking about trying to run on my LLY with remote filters then feeding into the stock filter finally.
I'm not sure what it runs but I'm thinking around 40ish psi.
Is this to much for the cp3 to handle? What would happen if I ran that much? Blow the seals out of the pump or?
 
Chevy1925

Chevy1925

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CP3 wont care but your FICM might. it may cause a lope unless you can turn the pressure down.

whats the volume on one of them? while pressure is one end to worry about, the volume to the pump is most important
 
mike diesel

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12 psi is usually max you want to run. I wouldn't even waste my time messing with the pump off a 7.3 and iirc they run more like 60 psi.

Has anyone ever looked at a ficm? All the fuel does is cool it. Fuel pressure does not affect the ficm at all as it is just a straight shot right through the ficm, in one end and out the other. Your FPR is what freaks out with high pressure. Lbz+ trucks lope just as bad with high fuel pressure and they don't have ficms.
 
Dirtymaxx03

Dirtymaxx03

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mike diesel said:
12 psi is usually max you want to run. I wouldn't even waste my time messing with the pump off a 7.3 and iirc they run more like 60 psi.

Has anyone ever looked at a ficm? All the fuel does is cool it. Fuel pressure does not affect the ficm at all as it is just a straight shot right through the ficm, in one end and out the other. Your FPR is what freaks out with high pressure. Lbz+ trucks lope just as bad with high fuel pressure and they don't have ficms.
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It does affect the FICM, and I personally know several people who run super high fuel pressure on their LBZ+ trucks
 
Chevy1925

Chevy1925

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mike diesel said:
Trying to learn here, how does it affect the ficm when it doesn't physically monitor in coming fuel pressure?
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dunno, you tell me. i ran 20psi to my FICM, i get a lope. bypass the fuel around the FICM and lope goes away. My truck is not the only this does this on as well. i dont think anyone has an exact reason as to why, like the posi-trac in the back of a dodge. nobody knows how it works, IT JUST DOES! :D
 
Operator1

Operator1

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I remember seeing pictures where someone took their ficm apart, the part that the fuel goes through was just an aluminum heat sink IIRC. The fpr on the other hand, just needs its operating voltage adjusted to compensate for the increased fuel flow to stop the loping idle. I have ran as much as 25 psi, currently running 18.
 
mike diesel

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Chevy1925 said:
dunno, you tell me. i ran 20psi to my FICM, i get a lope. bypass the fuel around the FICM and lope goes away. My truck is not the only this does this on as well. i dont think anyone has an exact reason as to why, like the posi-trac in the back of a dodge. nobody knows how it works, IT JUST DOES! :D
Click to expand...

I will stand corrected, but that voice in the back of my head won't let me understand it:confused::thumb:
 
mike diesel

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Operator1 said:
I remember seeing pictures where someone took their ficm apart, the part that the fuel goes through was just an aluminum heat sink IIRC. The fpr on the other hand, just needs its operating voltage adjusted to compensate for the increased fuel flow to stop the loping idle. I have ran as much as 25 psi, currently running 18.
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That's what I'm saying, I had mine off and all I could see is that its just a tube that fuel flows through. No sensors or anything.
 
SSchmi5519

SSchmi5519

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Oct 19, 2008
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All you want is positive pressure feeding the CP3 to get the benefit. It doesn't matter if it is 1psi as long as it stays there under WOT.

My Airdog 150 (older model) holds 11-12 at idle, and on the dyno at WOT it drops down to 2-3psi.

I would like to run a higher volume pump (gph), and keep the pressure low. The lift pump is there to supply the CP3 with fuel. Fuel does not compress(appreciably) so you do nothing trying to force more psi to the pump(except piss it off). You want to stay above 0psi so that you do not create a vacuum in the supply line and risk cavitation.

If you have rail pressure issues, increasing the CP3 supply from 5psi to 10psi isn't going to help you.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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Ill say this, i cant say anyone has proved too much PSI is bad for a duramax besides the FICM deal. Is it un-necessary above a certain point, yes. Our concern is volume with pressure being the next in line. there are a couple guys on here that are or use to run mitsu pumps up to 45-50psi IIRC.

if the volume is there in the 7.3 pump and trubbs you really feel like makin it work, i dont see why not. your FICM may need bypassing but thats all i can think of.
 
Jackblack99

Jackblack99

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The lift pump im going to be running is 200gph at 8-9 psi. I know my little brother had his front seal on the cp3 blow out with an airdog 150. I think it had more to do with the fact he had welded his big return manifold banjo bolt welded shut and return fuel backed up and created pressure because it had no where to go.
 
sweetdiesel

sweetdiesel

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SSchmi5519 said:
All you want is positive pressure feeding the CP3 to get the benefit. It doesn't matter if it is 1psi as long as it stays there under WOT.

My Airdog You want to stay above 0psi so that you do not create a vacuum in the supply line and risk cavitation.

If you have rail pressure issues, increasing the CP3 supply from 5psi to 10psi isn't going to help you.
Click to expand...

The single most important reason is the cp3 is lubricated via fuel, lack that and there is a 600 follar fuel leak
 
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