EFI Return Line?

[Ks65stang]

Can this port be used as a return line for EFI? If not, I will drill a hole in my new tank and use this fitting with another to attach an internal return tube. I do not want to consider running the return line inside the filler neck house. Thanks in advance.


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[Broncobowsher]

I would do the internal return tube.

The last EFI conversion I did I put a Holley Hydromat on a dedicated pickup tube. Used the original pickup as the return.

 

[DirtDonk]

What year is that tank? Never seen one (that I remember anyway) with only one tube. Is that a '70 by any chance? Or maybe a late '75?

But either way, you'd want to keep the original as an EVAP vent line to the charcoal canister. Or are you no longer planning to use a charcoal canister system to keep the fumes at bay?
Still have to keep some sort of vent plumbed into the system however, to keep expanding fuel and vapors (heating up during the day kind of thing) from puking out the cap or elsewhere.

Paul

 

[Ks65stang]

That is my old rusty tank from my 76 302/c4 wagon with one vapor port.

Above is my new LMC truck tank that has two ports. LMC’s ford warehouse is 10 minutes from my house! Didn’t know the tank came with two ports when I started this post. So now I’m using one of the ports for the return and the other to retain the existing vapor line and charcoal canister.

I’m using 50psi rated fuel hose on one of the ports and tying the open end low in the tank at the sending unit with a stainless zip tie. The return hose will not affect the float function. This took some time and work attaching through the sending unit opening but I got it eventually. I used a metal rod to stiffen the hose while I installed it and a long ratchet extension with a swivel to tighten the band clamp. The other port will still tie into the existing 76 emissions system.

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[blubuckaroo]

I'm installing a FI unit too, and according to my research, the supply and return mines should be the same size.
Also, it's better that if the return fitting is below fuel level so the fuel won't be aerated. Bubbles that get picked up by the pump will cause cavitation.

 

[DirtDonk]

Traditional returns were one size smaller than the feed. But a lot of modern systems use the same size for both. A lot of times it’s just 5/16 for both now, whereas in the old days they needed three eights to feed the hungry engine.

The single vent line on the 76 was, I believe, a one-year only item. At some point in 76 they changed over to the later charcoal canister system and eliminated the condensing tank from the cabin. Then in 77 they went to a completely different fuel tank, making the 76 a one year only item with the early metal tank but only a single vent.

 

[DirtDonk]

Interesting picture of the inside of the tank. Any chance you can still get a shot but one showing the fill vent tube on the other side of the filler neck?

 

[Ks65stang]

My supply and return lines are the same size except where the return line necks down at this tank fitting. This hope this better option than drilling a hole in a new tank. The rubber hose will be metal zip tied to the sending unit and the end will be at or near the bottom of the tank preventing aeration.

Sorry I can get any better photos of the larger vent tube. This was taken from an iPhone from the sending unit opening with a flash light inside the tank.

I will let you know how it runs in a long while….I have lots of other work also in progress. Before the tank and drivetrain are reinstalled, I have a moderate frame repair near the driver side leaf spring shackle hanger.


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[jamesroney]

I’m using 50psi rated fuel hose on one of the…

What kind of hose did you use? Are you aware that you must use submersible rated hose for anything INSIDE the gas tank? The outer jacket of almost all fuel line is not compatible with gasoline. Usually the jacket fails and turns into chunks of gooey black tar stuff.
On the pressure side…the jacket provides reinforcement. So you only get about a year before the aneurism ruptures. With your set up…you will be creating gunk for many years.

Gates has a submersible solution.
Don’t ask me how I know about this. (Paul already knows…)

 

[Broncobowsher]

That is true. Inside the fuel tank needs special submersible hose. regular hose protects the rubber from the inside. Submerged the rubber is attacked from outside.

Another thing you can do. Magnets. They can be used to hold stuff to the bottom of the fuel tank. I used them with a hydromat, but you can use them with a fuel hose.

 

[BPerry]

Watching this, as I'll be doing a complete efi conversion in upcoming months after a new exhaust set up.

Digging the clean setup ks65, I prolly won't go that route though.

Anyone have any issues with the return on the filler vent hose? Other than the potential aeration issue...

BP

 

[DirtDonk]

Some of the naturally helpful things about aeration are:
1. The fuel is being taken from the bottom of the tank and air is naturally trying to go up to the top.
2. The air will eventually dissipate into the gas as ever smaller bubbles, or up to the top to mix with the fuel vapor.
3. The sock filter tries to separate air from gas naturally. So the more gas in the tank, the less chance aeration can be an issue.
4. The fill-vent on a stock ‘71-76 tank is about as far away from the pickup as you can get without making a new location.
5. Making some kind of extension to put the return fuel down into the bottom of the tank is a fairly simple and basically ultimate solution. Except on a fill vent of course…
6. The motions of the vehicle and the vibrations from the stiff suspension not only can create a little of their own aeration naturally at the surface, but also will help to dissipate any aeration introduced by a return stream. Even the mild vibration from an idling engine and flowing fuel can probably encourage the dissipation as well.

I’m not saying that aeration can’t ever be an issue. Just that it might not be as bad as it sounds.
None of that is scientific of course, or based on personal experience. And we’ve had this argument before about how serious aeration can sometimes become. But I don’t know anyone who has had a bad experience with it.
And now that I said all that you’ll hear tons of horror stories about putting it in the fill vent!

Somebody needs to make a clear full size fuel tank to run on an EFI or even carbureted return system. That way you can install multiple points where the return fuel is entering at different places just to see how much aeration there actually is.

 

[BPerry]

Some of the naturally helpful things about aeration are:
1. The fuel is being taken from the bottom of the tank and air is naturally trying to go up to the top.
2. The air will eventually dissipate into the gas as ever smaller bubbles, or up to the top to mix with the fuel vapor.
3. The sock filter tries to separate air from gas naturally. So the more gas in the tank, the less chance aeration can be an issue.
4. The fill-vent on a stock ‘71-76 tank is about as far away from the pickup as you can get without making a new location.
5. Making some kind of extension to put the return fuel down into the bottom of the tank is a fairly simple and basically ultimate solution. Except on a fill vent of course…
6. The motions of the vehicle and the vibrations from the stiff suspension not only can create a little of their own aeration naturally at the surface, but also will help to dissipate any aeration introduced by a return stream. Even the mild vibration from an idling engine and flowing fuel can probably encourage the dissipation as well.

I’m not saying that aeration can’t ever be an issue. Just that it might not be as bad as it sounds.
None of that is scientific of course, or based on personal experience. And we’ve had this argument before about how serious aeration can sometimes become. But I don’t know anyone who has had a bad experience with it.
And now that I said all that you’ll hear tons of horror stories about putting it in the fill vent!

Somebody needs to make a clear full size fuel tank to run on an EFI or even carbureted return system. That way you can install multiple points where the return fuel is entering at different places just to see how much aeration there actually is.

So DD, I hear there's a sizable and nifty little company out in CA I hear good things about that could likely get one of the fabricators to mock up and engineer your proposal!

BP

 

[DirtDonk]

I have no idea who you might be talking about...
But I'll ask them anyway!

Paul

 

[Ks65stang]

Amazon.com

Thanks for the heads up on the rubber hose, I knew better. So I switched to PTFE tube. Slightly stretched the tube and installed and it’s on tight. Plugged one end and it held with 60PSI. I may still add a fastener if I can find one small enough.

Not sure this is even necessary but will prevent air.


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[DirtDonk]

That thing sure is purdy inside.
But now I see I never needed another picture from a different angle. I wanted to see how the tube entered the tank and the shadows I never even noticed in the first pictures that your fill vent tube was right there in plain site the whole time!
I haven’t peeked into many stock tanks, but I sure don’t remember the filler neck and fill vent being quite like that.

I’ll be very interested to hear how this tank fills at the gas station when it’s up and running.

 

[bteutsch]

I know you said you didn’t want to use the fill hose as a return, but this is what I use for both my main and aux tank. Works great

mor-65385_w.jpg

Moroso 65385 Moroso EFI Fuel Return Line Kits | Summit Racing

Free Shipping - Moroso EFI Fuel Return Line Kits with qualifying orders of $109. Shop Automotive Fuel Lines at Summit Racing.

www.summitracing.com

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[pcf_mark]

On my EFI first round I connected it to the fill because it was easy. I never had any aeration issues but I can tell you this - when it was getting low on gas (under 1/4 tank) you could HEAR the fuel trickling back into the tank. Sounds lie someone taking a leak into a steel bucket when I was sitting at a stop light!

 

[omureebe]

Just curious why not use a retrofit submersible pump?

I'm using a Hyperfuel Retrofit 40015 on my stock tank and FiTech. Works well and plumbed with AN fittings already. If I remember right, it sits 3/4" high, so my hockey puck lift kit was more than enough.

 

[bteutsch]

I used a walbro pump in my stock tank.. I trimmed the factory pick up tube/ sending unit and put the pump on that with a 2.5x8 Holley hydramat.


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