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 
Fass flow thru
- Thread starter LarryJewell
- Start date
I was unaware the FASS was a draw thru at all. I thought they were a positive displacement pump with no bypass containing a check valve which is what you need in order to keep it from leaving you on the side of the road. This can be internal or external.
Not sure what a draw straw is but if you are talking about a regular ol' aftermarket larger fuel p/u, then I can't see it making a difference.
Not sure what a draw straw is but if you are talking about a regular ol' aftermarket larger fuel p/u, then I can't see it making a difference.
I kill the pump with a switch right now in low fuel situations, I was wanting to know if I lose that ability when I add the draw straw kit since it will pickup from a new location.
Hey Larry im pretty sure when you add a draw straw you lose the flow thru feature you have now and you'll have to bypass the pump so it wont leave you stranded when you get low on fuel.
flow through is all in the pump, the pick up would have no effect unless there is something i am not aware of in the fuel line going to the tank but a draw straw is just a larger diamiter pick up tube, and larger sized line going to the lift pump .
My fass is not flow thru at all
Neither was the one I had but it was an older model. Maybe they changed something with the newer ones?
Ya now that i think about it i dont remember the Airdog or FASS being flow thru, i thought you had to use a bypass valave to keep the fuel flowin under 1/4 tank when your runnin a draw straw
I was under the impression that when you add a draw straw like that below 1/4 it begins to have trouble gettin fuel maybe because of the constant sloshing of the tank but theoretically if you have the draw straw cut to the right length this problem shouldnt be happening. But i still hear people complaints from people so idk
People with complaints likely did not cut the hose to the right length. With fuel slosh in the tank it would not matter if there was a bypass or not or if the pump was on or not. If it can draw air it will, regardless of how the fuel is being moved, and the end result will be the same.
Last edited:
I'd love to have a fass but all the people that have 1/4 tank issues have made me a bit leary about getting one.
Picture this if you will.
The stock pick-up on all trucks has a rubber foot at the bottom of it that literally sits on the bottom of the tank. It is flexible...as is the plastic tank your fuel is in....so it maintains contact with the tank floor no matter what.
Now add in a draw straw that does not have the foot on it which is rigidly mounted to the top of the tank. and some people have the 1/4 tank issue. (it's not Dmax specific)
Why ? Because the bottom of the tank flexes a bit from the weight of the fuel and causes a much larger gap between the end of the drawstraw and tank floor than when you initially installed it....and you don't have the rubber foot to flex and maintain that contact any more.
Just thought I'd throw that out there to address the 1/4 tank issues brought up in this thread.
To the OP...I'll pose your question to Dan at FASS and post his reply in here later.
The stock pick-up on all trucks has a rubber foot at the bottom of it that literally sits on the bottom of the tank. It is flexible...as is the plastic tank your fuel is in....so it maintains contact with the tank floor no matter what.
Now add in a draw straw that does not have the foot on it which is rigidly mounted to the top of the tank. and some people have the 1/4 tank issue. (it's not Dmax specific)
Why ? Because the bottom of the tank flexes a bit from the weight of the fuel and causes a much larger gap between the end of the drawstraw and tank floor than when you initially installed it....and you don't have the rubber foot to flex and maintain that contact any more.
Just thought I'd throw that out there to address the 1/4 tank issues brought up in this thread.
To the OP...I'll pose your question to Dan at FASS and post his reply in here later.