Borla 8 stack efi fuel problem

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Bob Stoeger

Ok hopefully I can explain this so you understand my problem. We got the system up and running and the return fuel line is in the back of the tank near the top.but after several minutes of running I had fuel rising up out of the fuel filler and all over the floor! The car is sitting on jack stands in the rear and on the floor in the front and the fuel tanks are 3/4 full. I know that now there is no place for air to escape with the car at this angle and if it was on level ground there would be no issue. But what happens when the owner fills the tanks to the top ? There will be no place for air or pressure if you please to escape! I'm stumped on this one ,anyone go through this that has an answer to help me out on this one.
Thanks guys
 

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B

Bob Stoeger

ckouba said:
It sounds like you may be pulling from one tank and returning to the opposite.

Is this a possibility? How are you plumbed?
Click to expand...
Hi Chris
Both tanks are teed together hen the fuel pump pulled from the center of the two tanks return line is in the left tank.
 
Joules5

Julian

Lifetime Supporter
If the pump is pulling from the center of the balance tube for the two tanks, then there is no chance for the tanks to actually balance and the left tank will fill. Even with a -10 balance tube on my Ultima I find it takes time for the tanks to reach equilibrium and I have to fill both tanks at the gas station. On the GT40 the tanks are independent with a pump for each.
 
blueovalz

Terry Oxandale

Skinny Man
I think Julian may have hit it, but to add detail, if you have two tanks 75% full, yet the draw from them is between a common line between the tanks, it is theoretically drawing from both by equal amounts, and returning to only one tank. After continuous running of the pumps, that one tank will eventually receive not only gas from it's own tank, but additional gas from the other tank as well, and now you're trying to combined both volumes into a single tank (150% of tank capacity, and hence the overflow. I Run mine the same way, but can turn one pump on at a time (a pump at each tank), and must remain cognizant of the level in each tank as I run each pump, or I will overflow the return tank if not careful. So why my setup then? It allows me to transfer fuel from my secondary tank to my primary tank (fuel return tank), thus I balance the car with depending on track direction.

BTW, would love to see what your fuel map looks like (as well as engine parameters).
 
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Ian Clark

Supporter
Hi Bob,

We experienced the same thing on the first 8 stack EFI system installed in 2004. It was a TMW unit (now part of Borla). On the CAV each bladder tank has two vulcanized nipples at the engine bay. Normally one per tank was used to pump the fuel to the carb(s). Piece of cake, no problems.

Most EFI systems have a return line to the tank so we used the second nipple for the return line. Worked fine at low RPM however on wide open throttle fuel would come up the filler necks. So I know where you're at.

The fix for us to extend the return line inside the tank from simply dumping (actually spraying) the fuel into the top of the tank to being submerged at the bottom of the tank and well away from the fuel pickup. Solved the problem. Hope this helps your situation.

Cheers
Ian
 
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Bob Stoeger

Canuk40 said:
Hi Bob,

We experienced the same thing on the first 8 stack EFI system installed in 2004. It was a TMW unit (now part of Borla). On the CAV each bladder tank has two vulcanized nipples at the engine bay. Normally one per tank was used to pump the fuel to the carb(s). Piece of cake, no problems.

Most EFI systems have a return line to the tank so we used the second nipple for the return line. Worked fine at low RPM however on wide open throttle fuel would come up the filler necks. So I know where you're at.

The fix for us to extend the return line inside the tank from simply dumping (actually spraying) the fuel into the top of the tank to being submerged at the bottom of the tank and well away from the fuel pickup. Solved the problem. Hope this helps your situation.

Cheers
Ian
Click to expand...
Ian,
This is something I've also considered after doing a little research, mine right now just sprays the fuel out from the top of the fuel tank like you said .So I'm going to do the same thing you did and extend the return line in the tank and go to the bottom of the tank with it ! I hope that works. Thanks
 
blueovalz

Terry Oxandale

Skinny Man
I forgot to ask, do you have a tank vent that should you overfill a tank, it will exit out a vent, with a small hose to ground level, rather then out the filler?
 
Big-Foot

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
Julian and Terry have given great advice / information.
Another thing to think about is in your return line. You should never just dump the return fuel into the top of the cell. Instead, your return line should have a tube inside the cell that brings that heated fuel to the bottom of the cell. Many of us have found out that to dump heated fuel (return line from the rail) into the top of the tank, it is aerated and much of it will go right out your vents....
 
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