# Fuel line return question



## Lawddog (Jan 2, 2020)

Hey Fellas, 
Got another question for everyone. So from what i have read on here having a return line is a good idea, and even though they were mostly on cars with AC, my car was plumbed with one. So hear is my question, I have gone out and spent alot of money on steel braided fuel line and inline filter from the stock mechanical fuel pump. I see that on the stock fuel filters with the return outlet, they are closer to the oultet side of the filter so is i put a T-in the fuel line after the filter before the carb for the return line, will that work, or will that just send fuen back to the tank and be useless. I also dont want to wast the money i have spend on the fuel lines just to take them off to incorporate the filter with the return line. 

I know its a weird question and i am trying to figure things out as i go. 

Thanks in advance, 
V/r Jason


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## Lemans guy (Oct 14, 2014)

You want to keep that fuel return to the tank to prevent vapor lock. There are a few ways to do it. One is with the fuel filter having one inlet and two outlets...the smaller outlet is the return to the tank. Just button hook the line and send it back to the tank.

you need the correct fuel filter, Wix makes one, available at any auto parts store.

the return can also come from a mechanical pump that has a return line built in, or you can run the fuel line in a fuel log past both bowls and then button hook a return line


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## PontiacJim (Dec 29, 2012)

First, so this is not forgotten, you will need to have a fuel sending unit for the gas tank which has the 1/4" return line feature. Not all sending units found on top of the gas tank have these. It would do not good to have the return line gong back to the tank and no hook up for it. These sending units can be easily added and most Pontiac suppliers, Ebay, and gas tank makers typically offer these.

I will add that the return line needs to be of a smaller diameter so that you do not lose fuel pressure going to the carb. It can be the 1/4" return line, the 3-outlet style fuel filter *Lemans guy* mentioned, or some other means that will add some restriction so as not to lose the needed fuel pressure.

So here is some general info that might be of value to you or anyone else doing the same thing.

Now as mentioned before, some of the factory fuel pumps will have 1 inlet (3/8") for the steel gas line coming in from your gas tank that is connected by a short length of rubber hose/clamps. Then you will see 2 outlets, one threaded fitting for the 3/8" for the steel line that would go to the carb (pressure side), and the 1/4" outlet used for the return line running right off the pump and gets connected to the 1/4" line going back to the tank with a short length of rubber hose/clamps. Photo attached so you can see what we are talking about. I did a search for Pontiac 400 with AC as not all the fuel pumps have the return line and I have seen different styles of the pump, all of which will fit and work. RockAuto has a good selection and you can also see all the different types: 2-line, 3-line, and late model larger can. These pumps would be compatible with ethanol laced gas as opposed to the factory stock which would be rubber diaphragms and will deteriorate over time and quit. 1968 PONTIAC GTO 6.6L 400cid V8 Fuel Pump | RockAuto

You can get an aftermarket fuel pump like the Edelbrock which will put out more flow over stock 110 GPH versus 40 GPH stock, but it only has an inlet and outlet. It does not have a return line built in. Photo attached of it. So this would be where you would use your application to install your "T" fitting or the 3-outlet style fuel filter.

If going with an electric pump of some kind, you still want a return line or bypass of some sort. Several ways of doing this and diagrams can be had by searching the internet.

Next up is the 1964-67 Pontiac fuel filter for AC & tripower cars. It has 3 connections - 1 inlet from the gal line coming from the fuel filter, one outlet connecting the filter to the carb, and the smaller outlet that connects to the fuel return line going to the tank. This is a repro to look like factory, but you can also get a generic one from most any parts store as they are a common style filter. With this type filter, you would mount it up near the carb using a mounting bracket to hold it in place and steady. So this shows you that you could mount your "T" fitting on the gas line going into the carb somewhere near the carb. Then run the return line down to the steel line going back to the tank. Photo of the filter is attached.


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## Lawddog (Jan 2, 2020)

Thanks a million guys...


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## Lemans guy (Oct 14, 2014)

Exactly!.....The wix fuel filter with return line is a ..........Wix 33041......


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## Shooter (Nov 7, 2015)

PontiacJim,
Man, I'm glad you're on this site! I'm replacing leaking fuel lines (they're REALLY old!), gas tank and fuel pump. Pontiac 400. I have a 1/4" return line and need it to go onto the gas tank. No bung to work with. In your first paragraph you mention a sending unit with a 1/4" return line. Have made 2 calls to Summit and they have no idea how to do this. Where can I get such a sending unit?
Thanks!
Shooter


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## PontiacJim (Dec 29, 2012)

Shooter said:


> PontiacJim,
> Man, I'm glad you're on this site! I'm replacing leaking fuel lines (they're REALLY old!), gas tank and fuel pump. Pontiac 400. I have a 1/4" return line and need it to go onto the gas tank. No bung to work with. In your first paragraph you mention a sending unit with a 1/4" return line. Have made 2 calls to Summit and they have no idea how to do this. Where can I get such a sending unit?
> Thanks!
> Shooter



Should be able to get one almost at any Pontiac parts supplier. Sometimes other non-Pontiac suppliers just don't have the sharp knowledge on some things. Summit is good, but it is better to know what you want in some cases.

Simply input your year car, the add "gas tank sending unit with 1/4" return line" and you should get severl hits - I just checked randomly. You will have a 3/8" outlet for the gas line and 1/4" return line in the description. Check InlineTube, OPGI, AutometalDirect, Ames, etc. and you should have no issues. * Replace* all rubber lines, and use a high pressure rated rubber hose used for fuel injection for your connections. IF you do not specifically ask for this at a parts store, they will give you an inferior rubber line and tell you it is compatible with ethanol gas. I found out on my S-10 that this was BS and 1 year later I had the same rubber hose gas leak with the same softened and swelled up rubber. I believe the fuel injection line states on the outer casing 100 PSI.

Your new fuel sender should also come with a new "sock" on the end of the 3/8" tube that goes into the gas tank. It should have a mesh looking quality to it. It acts as a first line filter for the fuel system going into the fuel pump. The originals can collapse, get plugged, or harden and become useless. I suppose not all senders have these based on repop manufacturer. If you can get one that is included, it won't hurt. If it does not have one, you can always add a fuel filter prior to the fuel pump somewhere along the line - just like modern cars do and they are usually located somewhere along the frame. You would have to cut out a section of gasline to match the width of the filter used, get it with rubber hose type nipples on the ends, and use short length of fuel injection rubber hose to attach. Then, like modern cars, you can replace it as needed.

On my brother's '48 International truck, I used a clear filter housing that has a metal screen in it so you can actually see inside if you have any debris in it. You can reverse flush it. Simple plastic and inexpensive - purchased from the auto parts store. This is for a 5/16" line, so do some checking on 3/8" line if that is what you have. Wix #33972 is a clear body w/screen. It would make a good pre-filter inserted between the gas tank and fuel pump and do what the internal "sock" does, except you can see it and replace it, unlike the "sock."









NapaGold 3972 (Wix 33972) Fuel Filter


Check out the deal on NapaGold 3972 (Wix 33972) Fuel Filter at FleetFilter - NapaGold by Wix, Fram, Baldwin, and Luberfiner



www.fleetfilter.com


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## Shooter (Nov 7, 2015)

O.K. Thanks!
I usually see the fuel filter between the fuel pump and the carb. Is this wrong? The fuel pumps are usually pretty robust and can pump through small stuff. It's the carb that's touchy. Wrong?


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## Lemans guy (Oct 14, 2014)

Yes fuel filter should be between pump and carb. They should not restrict flow and won’t unless really a cheap one. The needle and seat on the carb float has to be adjusted correctly and the pump’s pressure should be known and match the carb’s requirements.

A fuel regulator may or may not be needed, they were not used originally, but some guys change so much stuff they need to regulate the fuel pressure.


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## PontiacJim (Dec 29, 2012)

Shooter said:


> O.K. Thanks!
> I usually see the fuel filter between the fuel pump and the carb. Is this wrong? The fuel pumps are usually pretty robust and can pump through small stuff. It's the carb that's touchy. Wrong?



Yes, you are correct. I did not say to use the filter I suggested as a replacment for the filter between pump and carb. If Q-jet, it is typically inside the inlet housing where the line connects. Others carbs would use an external filter - your choice.

The replacment filter I spoke of is in place of the factory type "sock". Basically it is a strainer. The mesh filter I pointed out will not affect fuel flow anymore than the factory "sock". It will simply catch any larger particles like the "sock" except _you can see_ IF anything gets trapped AND it can be removed and replaced without pulling down the gas tank, or trying to figure out why your engine isn't getting enough gas which could/does happen with a "sock" on the end of the fuel pick-up inside the tank - should you own the car long enough to experience a gas supply issue.

It is just an option if whatever gas tank pick-up you purchase does not have the "sock" or if you choose to forgo the "sock" and add the strainer filter I mentioned - a little insurance that could save you some grief should you ever take a fill-up of gas and some crud were to be in it.

*Not required, just suggested.* I like options. Using an electric pusher pump back at the tank is another story all together - which is what I am going with and it gets a filter installed between the tank and electric fuel pump to prevent small particles from gumming up the electric pump. I am eliminating the factory fuel pump altogether.


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## BearGFR (Aug 25, 2008)

FYI, electric pumps usually require a bypass style pressure regulator with a return line that's the same size as the main fuel line. 

If your sending unit/pickup didn't have a provision for a return, you can get one that does from RobbMc. (I love his stuff and have all of it on my car) 
RobbMcPerformance 1/2" Sending Unit | 1968-1972 GM A-body
Bear


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## PontiacJim (Dec 29, 2012)

BearGFR said:


> FYI, electric pumps usually require a bypass style pressure regulator with a return line that's the same size as the main fuel line.
> 
> If your sending unit/pickup didn't have a provision for a return, you can get one that does from RobbMc. (I love his stuff and have all of it on my car)
> RobbMcPerformance 1/2" Sending Unit | 1968-1972 GM A-body
> Bear



Ya, I didn't want to get too deep into it, just provide an example of use.


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