Fass flow thru

othrgrl

Diesel Addiction Owner
Mar 10, 2008
2,151
4
38
Wilmington NC
www.mydieseladdiction.com
We have AirDogs with draw staws in a lot of trucks around here and never get complaints about 1/4 tank issues. I have raced with the low fuel light on with no decrease in performance. We have also run trucks with out the lift pump running and they draw fuel through them just fine for normal driving. We install them with the bed off the truck and the tank in and try to install them with under 1/4 tank and either notch the bottom or drill a cross hole in the bottom of the draw straw. The less fuel is in the tank, the less the tank is flexing so with less fuel your straw gets closer to the bottom.

I would also say that people that get 1/4 tank issues did one of 2 things:
They didn't leave the straw long enough or put it into one of the lowest parts of the tank.
or
They bent the fuel float's arm while removing their sending unit and their gauge reads 1/4 when they actually have less.
 

UNBROKEN

New member
Mar 30, 2008
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When you install a draw straw and get away from the factory pickup, does the Fass cease to be a flow thru pump, what i'm getting at, is if the pump dies for some reason, is the truck dead now :confused:

Quote from Dan at F.A.S.S. : Nope...should not make any differance. SHould flow though as normal. NOW if its an HPFP.....it will not flow though no matter what.
 

LBZ

Super Moderator
Staff member
Jul 2, 2007
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Quote from Dan at F.A.S.S. : Nope...should not make any differance. SHould flow though as normal. NOW if its an HPFP.....it will not flow though no matter what.

A what now? What model of FASS is this?

In a GM there is no "foot" as you called it. They have a small open top resevoir inside the tank that the factory p/u sits in which acts as a reserve so to speak in the event of sloshing. This hangs off of the top of the fuel tank from the fuel p/u "flange" for lack of a better term. When you remove this to install a larger p/u, there is no reserve to protect you from this slosh anymore so to speak and if you run your tank down, you can suck air. If the hose attached to the p/u was not cut to exactly the right length, you may run-out of fuel before the gauge says you should. Or if it is too long, the suction can actually make it get stuck to the bottom of the tank. Just things I have seen happen.
 

Whitetail Addict

Rockin' the stock tune
May 8, 2008
2,350
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South Central Pennsylvania
I was under the impression the FASS and Airdog were not flow through pumps:confused:

Maybe the air/fuel seperator style pumps are not flow through, but just the lift pump is?

Maybe I misinterpreted the info, but wouldn't the tank "bounce back" with more fuel out of the tank, thus eliminating the flexing of the bottom of the tank as the culprit of the fuel pickup problem?
 

Duramax_JP

Active member
Jul 3, 2008
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I was under the impression the FASS and Airdog were not flow through pumps:confused:

Maybe the air/fuel seperator style pumps are not flow through, but just the lift pump is?

Maybe I misinterpreted the info, but wouldn't the tank "bounce back" with more fuel out of the tank, thus eliminating the flexing of the bottom of the tank as the culprit of the fuel pickup problem?

I was under the same impression.


That would make sense also, since with less fuel there is less flex in the tank
 

Duramax_JP

Active member
Jul 3, 2008
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Ohh so if i run the regular FASS 150/150 with filters this problem should not exist according to Dan?
 

LarryJewell

Back with his honey :)
Jan 21, 2007
10,152
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San Angelo
pics from the install yesterday :D

all we used was a billet pickup, we retained the fuel return that Fass recommends to the filler neck. The return line that has been in place was a restriction to the the previous install (I had no part of) but the line was not run properly and had a pretty good kink in it as well as did the line from the tank to the input side of the fass. I originally saw these kinks after the install and rednecked them open I thought with pressure from zip-ties at the bend, but after pulling these lines the restriction was obiviously still there. I think these restrictions were the cause of the bouncy needle on my fuel pressure gauge, it doesnt do this anymore.

What I dont like about the billet pickup kit for the lly is this: notice in one of the later pics, the cool looking blue and red an fitting, the lly doesnt use this, but I got to pay for it anyway :(, evidentally the lly and lb7 shares the same kit, and the instructions dont come out and say that its not used either, I was smart enough to print instructions from several vendors, I found on "Kennedys" instructions that the lly uses the vent tube fitting instead of the supplied fitting "I think it was the vent tube fitting anyway, you just reverse two of the fittings and the biggest one becomes your pickup location. Anyway, you cut the new supplied fuel line to 9" (why in the hell doesnt it come cut to 9" from the vendor) :confused: and use a hose clamp to attach it to the top factory fitting and the other end is attached to the billet piece that fits in the cup. After looking at the plastic portion in the cup, I bet if somebody wanted to be cheap they could remove the bottom screen portion of the stock factory piece and have the same thing (better pickup capabilities) without spending money.

Anyway, we got it back together, it now has a 5/8" hose from the pickup to the Fass unit and all new 1/2" lines out of the Fass to the fuel cooler. I bought new 45* an fittings for the Fass from Jegs to help get smoother bends in the fuel lines to keep from getting any kinks this time. My original lines were +/- 4 years old and in bad shape, lots of wet spots on the old lines.

Once everything was in place the truck fired up pretty quick, ran for a minute and died. I did bring the truck to the shop with about 5 gallons in it, anyway it died on an incline, pumped the filter housing and got it started again and drove about a block, died again. Went & got 5 gallons of fuel in a jug and filled it to the truck, drove two more blocks and the truck died (probably air in the lines), got it started without priming and made it to the filling station. Its been running fine ever since.

I'd like to thank Alligator for the Pickup, and Larry (68Skylark) and Chad (one of my buddies) for helping with this install. Larry provided the shop with the lift and he did the actual install of the billet parts in the pickup :hug:
 

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sweetdiesel

That's better
Aug 6, 2006
10,390
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52
Thailand
I think you where smarter to take the bed off. I didnt do that and had a 1/2 tank of fuel in the sucker.....It was kinda a pain in the butt and lots of dirt every where.

I never noticed a difference.....But just looking at it,You can see the resritctions in the cup.
 

dmaxn04

New member
Mar 1, 2009
186
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Ocean Springs, MS
So you were orignally pulling your fuel from the stock pickup location, and returning in the filler neck. So only changes you made were installing a Billet Pickup? You didn't install a draw straw in the tank? Can I ask why?
 

LarryJewell

Back with his honey :)
Jan 21, 2007
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San Angelo
So you were orignally pulling your fuel from the stock pickup location, and returning in the filler neck. So only changes you made were installing a Billet Pickup? You didn't install a draw straw in the tank? Can I ask why?

we thought/think the problem may have been with the restricted lines, so we're taking it one step at a time, if this cures it without cutting the hole in the tank, so much the better.
 

LarryJewell

Back with his honey :)
Jan 21, 2007
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San Angelo
here's final pics until I clean up the line routing later today :D
 

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