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Fuel return line specifics

D

diamond

Well Known Member
I am building my tanks and want to plumb them for the possibility of EFII in the future. I have read many threads on this, but can somebody give me the specifics of which fitting to use on the 9. Fitting and location. Photos would be helpful. Thanks.
 
I would use the same type and size fitting as the standard fuel line - 3/8".

If you are just putting in a line to return fuel from a purge valve, then this can be the same size as the fuel vent lines - 1/4".

As for location, I would keep it near the stock fuel line location, which is on the access plate, unless you are going to have the fuel return line plumbed with a short tube over to another bay in the fuel tank. Doing that seems needlessly complicated to me.
 
Fuel Return

Hi Diamond,
The return fitting should be at least three inches from the fuel pickup so vapor bubbles can percolate out of the return fuel stream.

If you put in an additional -6 bulkhead fitting forward of the tank access, you will be good. In the middle of the round stamped stiffening feature in the root rib is a good spot.

Robert Paisley
EFII
 
I used 3/8" line and -6 fittings, and piped it internally in my tanks to the second bay so that any foaming or bubbles would not be caught up in the main fuel pickup in the first bay.
 
The EFII system states that the fuel return and the fuel pickup needs to have 4" of separation so that air bubbles are not entrained into the fuel supply. 3/8" return line size. Here is a picture of how I installed mine. I did not use any additional tubing to go to the next bay. I consulted Robert when doing this.

FP20022015A0002K.jpg
 
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Thanks guys. Is there any merit to dumping the fuel into the tank with a 90 degree fitting, as opposed to straight, as in the above photo? Also, is there any risk of the whole fitting rotating when tightening the fuel line to it? In some threads, I saw where a bung or plate with threaded hole was riveted in place. Do you think that approach is overkill?
 
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Hi Diamond,

I just went through the "rotation" issue you describe when putting a fuel return in my '10 tanks. The easy answer is "yes" you do have to worry about rotation. If you put the fittings fixed nut on the outside of the tank, there is much less of worry. I built an small anti-rotation bracket to protect against this regardless.
 
Yes, use the anti-rotation bracket. You'll want to puke if you tighten the outside B-nut at some point in the future and the fitting turns, breaking the seal of the Proseal around the fitting and producing a leak.
 
Bulkhead fitting

One simple solution would be to install the bulkhead fitting so the nut & washer are inside the tank. This way 2 wrenches can be used effectively to tighten the flare nut & prevent the fitting twisting the sealant loose.
Of course this won't protect the sealant if someone exerts excess force and neglects to use the second wrench, the locking plate method won't hold up either in this situation.
 
airguy said:
Yes, use the anti-rotation bracket. You'll want to puke if you tighten the outside B-nut at some point in the future and the fitting turns, breaking the seal of the Proseal around the fitting and producing a leak.
Click to expand...

Now that's funny! so did you make a mess?
 
bret said:
Now that's funny! so did you make a mess?
Click to expand...

Hah! No, I actually avoided that scenario myself, but only because I watched another builder suffer through it just before I got to that point. I did have this problem with my firewall pass-thru, but not my tank fitting.

There are three kinds of people in this world. Those that learn from listening, those that learn from watching, and those that have to pee on the electric fence themselves before they fully understand.
 
I guess you can count me as one who has peed on the fence. It still stings :) I didn't research thoroughly enough to realize that I was about to relieve myself on a hot wire!
 
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