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Discussion Starter #1
I hear with the HPFP setups like FASS and AirDog, your fuel pressure is around
Idle 17psi
Wot 14-15psi

But what should a good condition stock LP be at??? what are the psi's that are considered to be a good LP?


I just bought a 99 cummins and it is at 5-7psi idle and it goes down quick...
 

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u should be around 15ish

mine is around 8 at idle and i can peg it out at wot just like u. lol

im installing the raptor tomorrow.

get it fixed quick or else youll be dishin out lotta $$$ for a new injection pump.
 

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befroe I put my fass HPFP the lift pump i had iin the stock location when it was brand new right outta the box for the first five minutes it idles at 15 psi..... then dropped to 14 psi and once in a while spiked to 15 psi for a secound or to and at wot it dropped to 8 psi or so... after a couple of mounths the idle went to 12 psi and at wot went to about 6 psi.... then before i put my fass in the lift pump was idle'n with about 9 or 10 psi and at wot dropped to 3!!!!! after that i put my fass in...... now with the fass at idle its at 17 psi.... sometimes jumps to 18 psi for a secound or to and at wot i cannot get it below 12 psi I love my fass
 

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Another pump option would be an Airdog. They're about the same as a FASS only quite a bit cheaper
 

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If you are dropping below 7 to 8 psi at throttle, you need to make some changes. Even relocating the stock pump to the frame rail by the tank will make a big difference.

I'm running a Holley on the frame rail, and run about 17 at idle, 15 crusiing and 11 to 12 at WOT.

Ops
 

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Discussion Starter #7
Now I have a question??? on my gauge ut has about a 1/8" from where the needle starts to where zero is...

and it is about a 1/8" sweep from 0 to 10 psi

this is a liquid filled mechanical gauge a marshall which are usually good gauges.

when the truck is idleing it moves to the 0 and when you touch the pedal it goes back to where the gauge rests when truck is off which is below zero.

I don't know if that makes sense to you guys but the gauge goes from 0-100psi it is all I had laying around and is brand new so I don't really know if it has pressure or not.


My next question is you can drive the truck around fine and get on it a little before it defuels. is there any way to tell if the vp44 is going to survive with the new lp? what I am asking is if there is anyway to test it to make sure nothing was damaged? I am no longer driving the truck either.


My delema is I have a 30 day warr. but if it just the lp I want to upgrade it anyways I might as well just buy a air dog or FASS but I don't want to buy the LP and then the VP44 is bad and they won't want to fix it. but the truck runs and drives fine untill wide open
 

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My truck has had 2 factory lift pumps and I finally upgraded to the Airdog after I noticed exactly what you are describing. I am still on the original vp44 with 102,000 miles. I had to mess with my water seperator valve on the stock filter housing so I just went with the Airdog 100 and eliminated the stock housing as well. For 500.00 I got everything needed from Airdog and it came with a lifetime warrantee. You cant beat that.
 

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Now I have a question??? on my gauge ut has about a 1/8" from where the needle starts to where zero is...

and it is about a 1/8" sweep from 0 to 10 psi

this is a liquid filled mechanical gauge a marshall which are usually good gauges.

when the truck is idleing it moves to the 0 and when you touch the pedal it goes back to where the gauge rests when truck is off which is below zero.

I don't know if that makes sense to you guys but the gauge goes from 0-100psi it is all I had laying around and is brand new so I don't really know if it has pressure or not.


My next question is you can drive the truck around fine and get on it a little before it defuels. is there any way to tell if the vp44 is going to survive with the new lp? what I am asking is if there is anyway to test it to make sure nothing was damaged? I am no longer driving the truck either.


My delema is I have a 30 day warr. but if it just the lp I want to upgrade it anyways I might as well just buy a air dog or FASS but I don't want to buy the LP and then the VP44 is bad and they won't want to fix it. but the truck runs and drives fine untill wide open
Same thing happened to my brothers 02 DRW 3500 QC. LP was going, gone and went. We replaced it and we think no damage was done. That was 5k miles ago. We can onlly hope its OK. If it runs hard after new pump then we can assume it is good I guess.
 

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If you have any doubt whatsoever that your fuel pressure is low then get it checked out. Low fuel flow will burn up the injection pump which is about a $1500 fix. I know from experience.
 

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Here is the minimum pressure required for the 2nd Gen trucks! Anything below 10 PSI is asking for troubles...

I lost my first VP44 at 8-9 PSI..:w:

Here is the fuel pump testing...
Lift Pump Diagnostics
 

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Discussion Starter #12
thanks for that info...

and yes I hooked up a gauge and have maybe at the most 1psi it is more like .5psi so I am not driving my truck because I don't want to lose the vp and airdog is going to be coming very soon
 
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