Big Inches

Made my own draw straw, but noticed today, after I added my fuel pressure gauge that when tank is around or below 1/4 full, if you hit the brakes hard, or trun sharply it looses prime and fuel pressure bottoms out...Is this typical of the draw straw setup? I was thining about making a bowl around the inlwt maybe 6 inch or so in diameter and drilling some 1/4 holes around it to keep the inlet flooded, kinda like the way the in tank fuel pumps are made. any suggestions?? The way my draw straw is made is pretty much a 3/8 pipe with 3/8 NPT on each end. On the inlet side, I just added a 3/8 union maybe 2 inch long and drilled a series of holes around it (think 4) in which the holes are 1/4 to half inch from the bottom. The union is against the bottom of the tank.

Tate

Do you still have the stock fuel tank module? My Vulcan draw straw is in that, been down to the about 1/16 of a tank, and its still never sucked air or ran dry on me.

2141pete

I have the same problem. I put mine in too far forward on the tank and I think a little too close to the botom. WHaere did you put it at in the tank?

j-fox

Quite a few of us report that the bottom 1/4 tank is not usable with a larger pick-up tube.
It isn't needed on a street truck.

Diesel Doc

I can run down to 1/8 with my half inch draw tube but it does fluctuate after 1/4 when accelerating. I am going to set up something different soon also

2141pete

A tank with baffles would help alot I would think. I think the bowl Idea in post #1 would be a really good Idea but it would have to be something that could have move enough fuel through it and still have small enough holes to retain fuel in the situations like braking that let the pump lose prime. I thought about using 2 draw straws and a T but one could still loose prime and I dont know if the air seperation on the pump could get rid of all of it.

b4wheeler

I have the draw straw from Vulcan and have the same problem. I am looking for a replacement fuel sender module to place in my tank and use the pickup from that. I don't know if my pick up is in the wrong place or to high, but anything lower than 1/4 tank and my fuel pressure gauge will bounce off 0psi on hard stops and quick starts.

2141pete

Mine has actually died on me twice stopping at 1/8 tank. I takes forever to get the dang thing started again too!!

Fishin2Deep4U

Been running the first Draw Straw ever released and still have yet to run my truck out of fuel or have loss of fuel pressure.

I am working on a couple of things that may help the guys that report loss of fuel prime. Hopefully it'll be cheap enough for anyone to make, be functional and put everyone's fears to rest.

Dave

dzlfarmboy

I've had issues as well, It seems that most people with high volume FASS or AIRDOG's seem to have the most problems since they have to suck and circulate so much fuel voulume.

bent valves

I am running a homemade -10 AN (5/8”) draw straw placed near the back of the tank and only about ¼” off the bottom. If I brake heavily with low fuel it will occasionally suck air when the fuel sloshes forward. So I have been thinking about making a modification to my draw straw by adding an inertial valve that will suck fuel from the deepest point in the tank. This valve should work when braking, accelerating, climbing or descending hills. It is still in the thinking stage but should not be a nightmare to make and try out.

The diagram below is what I am working on. This valve will be placed inside, at the bottom of the tank under the draw straw. There is one tube extending to the front of the fuel tank and another toward the rear and these tubes will be at the bottom of the tank. In level, steady state going fuel can enter the draw straw from both front and rear because the weight will keep both sides open. The double red arrow is the valve and can move horizontally to close off either side. The green dot on the black weight is a pivot pin to allow the weight to swing. The yellow dot is a movable joint to allow the valve to operate.

So now if I accelerate or climb a hill the weight swings rearward and closes the front pickup tube off and fully opens the rear tube to suck up the fuel that has sloshed back. If the front of the tank is dry, the front tube is still filled with fuel, ready to go when the inertial event is over.

I am thinking of turning the cone shaped, red valve piece out of lightweight delrin (acetal) plastic. And making the weight out of brass. The valve would be about a 2” cube with ports for AN fittings.

Am I all wet or does this make sense?

2141pete

Dand man your smarter than me. I would never be able to make something like that.

Fishin2Deep4U

This is very much like our marine multi pickups. And they swing to follow the fuel as well. Wild stuff.

You can also look at a thing I have always called a fluid air lock. Basically, it stays open with fluid and locks closed as soon as it gets any air. I have tested a tank with 3 of these and it worked well, but added way too much complexity.

I am playing with a spare tank right now to see if I can coax it to a semi sumped shape. Using an old desert racing gas tank trick. But the new system I have drawn up a few days ago has tons of promise and may stop most issues.

Dave