Sump or Not

BlkMax

Member
Sep 1, 2008
743
4
18
Wasilla, AK
I could never get the air out and get them to prime. I always had to force compressed air into the filler neck to get the air out of the filter to get them to pump


The trick is to mount the Kennedy's in the vertical so they can't trap air. The first install I used the stock filter head to get the prime. After that, just replaced my filters one at a time and then let the pumps run. I also have small valve and some oil pressure tubing on the top of my stock filter head for easy bleeding. I also change filters with a full tank of fuel.
 

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Dozerboy

Well-known member
Jun 23, 2009
4,917
496
83
TX of course
I love my Kennedy pumps. Over 100k on mine and I'm having issues with them, but after seeing all the crap in my fuel tank its not a suprise. They still work for the most part. I do think someone's pulling your leg tell you 2 pumps can support 1000hp though. On my truck tune only they couldn't hardly keep up. With a stroker pump now over 50% throttle I'm sucking fuel through them.

Sent from my SAMSUNG-SM-G900A using Tapatalk
 

PureHybrid

Isuzu Shakes IT
Feb 15, 2012
3,517
501
113
Central OH
I love my Kennedy pumps. Over 100k on mine and I'm having issues with them, but after seeing all the crap in my fuel tank its not a suprise. They still work for the most part. I do think someone's pulling your leg tell you 2 pumps can support 1000hp though. On my truck tune only they couldn't hardly keep up. With a stroker pump now over 50% throttle I'm sucking fuel through them.

Sent from my SAMSUNG-SM-G900A using Tapatalk

Stock or aftermarket pickup? Pretty sure John's truck makes over 800rwhp with the twin setup.
 

PureHybrid

Isuzu Shakes IT
Feb 15, 2012
3,517
501
113
Central OH
The trick is to mount the Kennedy's in the vertical so they can't trap air. The first install I used the stock filter head to get the prime. After that, just replaced my filters one at a time and then let the pumps run. I also have small valve and some oil pressure tubing on the top of my stock filter head for easy bleeding. I also change filters with a full tank of fuel.

How old are your pumps? Mine have a blue housing
 

Robby Avery

GM TECH @ FENDER GMC
Jul 31, 2008
820
2
18
Norman Park, Georgia
Kennedy twin pump filter combo kit here had mine since 2006 and never had a problem with them dead silent and the kit came with mount fasteners pumps plumbing and two filters follow the install instructions mine sits on the bottom of the tank and never given any issues it's a 5/8 pick up and never hesitates when I hit the go pedal even with twin cp3 :thumb:
 

Hambone

Always learning
Jan 24, 2016
572
0
16
Florida
Are you saying the sump isn't needed for performance reasons or because you have never had any startup issues at or under 1/4 tank?

Yes.
The stock sending unit has a plastic bowl that sits close to flat on bottom of the tank. The stock draw line is inside this bowl as well as the return line so especially the bowl always has access to fuel In low fuel conditions and heavy acceleration or braking.
Now add the fuel pump... it’s flowing 2-4 gallons a minute It’s going to drain the bowl faster than it can be refilled.
The sump is a gimmick because the avg Joe can get away with just modifying the existing unit
Performance world where your avg Joe try’s running the 1/4 with a gallon of diesel is going to have problems or he could spend money on a sump
Performance world where your running a custom fuel tank, sure a sump is good or just fab a built in one and add a baffle to help sloshing

Anyways just my .2
Some guys spend 25k to run a 10
Some guys spend 5k and with help from a sawzall get a 10
 

OregonDMAX

NOT IN OREGON, NO DURAMAX
Apr 28, 2013
3,964
8
38
36
Goodyear, AZ
Yes.
The stock sending unit has a plastic bowl that sits close to flat on bottom of the tank. The stock draw line is inside this bowl as well as the return line so especially the bowl always has access to fuel In low fuel conditions and heavy acceleration or braking.
Now add the fuel pump... it’s flowing 2-4 gallons a minute It’s going to drain the bowl faster than it can be refilled.
The sump is a gimmick because the avg Joe can get away with just modifying the existing unit
Performance world where your avg Joe try’s running the 1/4 with a gallon of diesel is going to have problems or he could spend money on a sump
Performance world where your running a custom fuel tank, sure a sump is good or just fab a built in one and add a baffle to help sloshing

Anyways just my .2
Some guys spend 25k to run a 10
Some guys spend 5k and with help from a sawzall get a 10

The fuel return goes right to that bowl so the lower the tank gets the more returned fuel goes into the bowl which is just all foam. The stock bowl is a great design just not executed well enough imo
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,743
5,911
113
Phoenix Az
The fuel return goes right to that bowl so the lower the tank gets the more returned fuel goes into the bowl which is just all foam. The stock bowl is a great design just not executed well enough imo


You need to take a better look at what’s coming out of your return line. If you have foam, that’s a problem.

All returned fuel goes to the bowl. It’s dropped in at the very bottom of the bowl. Doesn’t matter how low it gets as the trap doors will keep tank fuel mixed with return fuel
 

04chase

Member
Mar 28, 2008
222
1
18
so what about shimming the rail vs the ppe race plug, which is the way to go there?

shim is near free , just need some ss washers and a m20x1.5 nut to install. i like the idea of not having max pressure all the time . The myth of running max psi at all times is hard on the injectors but not sure i have read many stories from someone losing injectors directly related to running a plugged rail . Some may find it hard to shim vs directly swapping but if you have the ability , i think most would sway shimming .
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
4,224
1,326
113
Larsen, Wisconsin
I have a FASS 150 with a RCD sump on my tow rig. I love this setup and it is reliable.

My built motor truck has a custom Fuelab setup with a RCD sump and will 100% agree that it is arguably the best right now. Pump is quiet, puts out tons of fuel, has an option for speed based on a mechanical switch or hobbs switch, and is comparable install wise to a FASS/Airdog.



Personally I like sumps for 3 main reasons: 1) they are faster to install than a draw straw, 2) they allow gravity to help prime the fuel system, 3) they offer a convenient drain if you get terrible quality fuel/contaminated fuel.
 

2004LB7

Super Moderator
Staff member
Dec 15, 2010
7,108
2,215
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Norcal
they allow gravity to help prime the fuel system

I beg to differ, the fuel level is no higher with the sump. With the filters and HPFP above the tank the level to pull the fuel is the same. Drawing from thw top or drawing from the bottom makes no difference in the pressure provided by gravity
 

Bdsankey

Vendor
Vendor/Sponsor
Feb 1, 2018
4,224
1,326
113
Larsen, Wisconsin
I beg to differ, the fuel level is no higher with the sump. With the filters and HPFP above the tank the level to pull the fuel is the same. Drawing from thw top or drawing from the bottom makes no difference in the pressure provided by gravity

You minimize vertical hosing runs is the benefit.

All of my runs to the pump are below the top of the tank.
 

2004LB7

Super Moderator
Staff member
Dec 15, 2010
7,108
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Norcal
just saying, the lift needed to reach the filters/Pump is the same for both and vertical runs are almost negligible when it comes to pressure or vacuum needed to move the fuel for priming

I don't want anyone else reading this thread thinking that somehow the weight of the fuel in the tank is going to create pressure to help prime with a sump when it wont. that's all
 

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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,743
5,911
113
Phoenix Az
just saying, the lift needed to reach the filters/Pump is the same for both

usually the pumps inlet is mid tankish. either way, im agree with you as once the fuel is below the pump inlet, its no longer gravity fed.

its really a mute point for the fass, airdog, and fuel lab. they have no issues under a draw situation. the Kennedy's and other fuel pumps like it (holley and so on) CAN have issues drawing "uphill" so to speak as they are not really designed for it.

the only time i worry about a sump, pump design and line routing is in a race application. You have much more freedom to setup the system to work 100% correct since your constraints change IE: could use a different chassis, fuel tank/cell, pump location, line location, no bed, and so on.

again, this "benefit" is extremely minor since the fass, airdog, and fuel lab all have the ability to use the stock pick up (no cutting or dropping of the tank) and will supply enough fuel for 1k hp.