Fuel Return System

[joe_db]

I am curious who else has set up some kind of fuel return line.

[joe_db]

My system has a valve in the return line that is cracked just a very tiny bit. I got the idea from my friend's 69 Corvette that has a tiny pinhole washer that controls fuel return after the mechanical pump.
It has totally eliminated a vapor-lock issue I was having and also makes priming a new filter easier.

[ndutton]

I do (but you knew I would). I use it for carb priming, new filter purging, fuel polishing, fuel transfer from one tank to the other, fuel tank emptying and finally as a fuel shut-off immediately ahead of the carburetor.

[joe_db]

Looks like only the two of us. I wish I had done it years ago, the "get the air out of the filter boogie" thing is only a trivial issue now.
I have given some though to getting one of those Facet pumps that shuts the fuel flow off when not energized to only let fuel recirculate when needed, but so far the simple valve arrangement is doing the trick.

[ndutton]

Y'know Joe, I don't get it. Since installing my system it has been a G-R-E-A-T improvement to fuel management for all the reasons I listed earlier yet it has elicited barely a yawn on the forum.

Oh well, I've got mine and enjoy the benefits.

[Bryan Janeway]

Very curious!!

Good day and thank you for reading,

I am very curious about the material used for the return line!! Are you using standard 1/4 fuel line for the return?? I see you can feed from either tank but only return to the 12 gal tank. I suspect you have to be cognizant of not drawing fuel from the 25gal tank when the 12 gal tank is full??? Also do you leave the return slightly open to prevent air from building up in the fuel line at the carb or do you keep it closed?? Also can you keep both fuel tanks open and draw from both at the same time?? Also the fuel tank fitting for the return… is that going through the inspection port cover or did you put it through the tank itself??

I am noticing on my northern 29, after motoring for three or four hours the fuel pressure warning will go off. If I go to full throttle for a 30 seconds or so the warning will go away and I’m good for another hour or so before I have to repeat.

Clearly I am sucking air from somewhere but I have resealed and dressed all my fittings and barbs. I was thinking of clearing out the fuel lines and doing a positive pressure check to see if I can find the leaky fitting. Thinking that adding a return line may help with the buildup of air.

My plan for the future is to replace my 12 gal with a 19 gal moeller tank. If that works as planned I would then like to install a second 19 gal tank in the opposite locker. Currently with the 12 I keep two Jerry’s on deck to supplement. On Georgian Bay I always seem to be motoring directly into a headwind or at best motor sailing. It is interesting how quickly 12 hours of gas disappears when you are trying to get somewhere. A dual tank system like this I think would take a lot of my worry out of the equation and remove the need to haul Jerry’s on deck.

Thanks for any info.

Best regards,

Bryan

[ndutton]

I am very curious about the material used for the return line!!

Current standard fuel line, A1-15 alcohol rated.

Are you using standard 1/4 fuel line for the return??

Yes, all of my fuel lines are the same size, 1/4".

I see you can feed from either tank but only return to the 12 gal tank. I suspect you have to be cognizant of not drawing fuel from the 25gal tank when the 12 gal tank is full???

Yes, the fuel gauge provides the necessary information. I have a switch for the gauge to read from either tank. To avoid reading the wrong tank the switch is a three position ON-Off-(ON). To read the 25 gallon tank the momentary position of the switch must be held on.

Also do you leave the return slightly open to prevent air from building up in the fuel line at the carb or do you keep it closed??

The valve is three position directing fuel either to the engine or to the return with an off position between the two. It's either-or, no bleed through.

Also can you keep both fuel tanks open and draw from both at the same time??

No, either-or.

Also the fuel tank fitting for the return… is that going through the inspection port cover or did you put it through the tank itself??

My 12 gallon tank was originally fitted with a separate unused port that I used to return the fuel. However, if you don't have such a port, the vent can be used. This thread is lengthy but discusses many of the details including using the vent as a return (about 50 posts in).

Clearly I am sucking air from somewhere but I have resealed and dressed all my fittings and barbs. I was thinking of clearing out the fuel lines and doing a positive pressure check to see if I can find the leaky fitting. Thinking that adding a return line may help with the buildup of air.

This sounds to me like a work-around addressing the symptom rather than the real problem.

[joe_db]

That is the issue, why does someone need a return line when the engines didn't originally have them?
IMHO some combination of a different fuel pump, different fuel line routing, and/or different fuel formulations is giving me vapor lock when I did not have it way back in the day.
I took my inspiration from my friend's old Corvette that has a tiny pinhole in a T fitting feeding fuel back to the tank, it works for the car and it works perfectly for me.
I had pretty much got to my limit of replacing and rearranging things and not getting any improvements, YMMV.

[joe_db]

My plan B that I thought of doing for fuel recirculation was to use a pump to suck fuel through the system that had positive shut-off, i.e when the pump is not energized it shuts off. This would be a push-button for air/vapor bleeding instead of always on.

https://www.pegasusautoracing.com/productdetails.asp?RecID=32334

Besides for costing more, I am not 100% sure the shut-off is designed for pressure-side applications and it adds a new layer of malfunctions, so I never got around to it.
Speaking of, this would be a great main fuel pump for a boat with the auto shut-off except for worrying it would get stuck shut.

[ndutton]

That is the issue, why does someone need a return line when the engines didn't originally have them?

It depends on what you want the system to do. I use my system for dry filter purging, fuel polishing and fuel transfer from one tank to the other. In all cases a good flowing tank return is needed. I do not use it when the engine is running. At those times it's one tank connected to the engine and that's it.

[tenders]

I’m afraid I don’t understand the problem this is trying to solve. I have no complaints with fuel flow in my single-tank, non-return system - not in operation, when changing water separator filters every few years, or when doing any other maintenance. Maybe this is more for the fancy-pants multiple-fuel-tank types.

You guys enlightened me to the benefits of a fuel pressure gauge many years ago - now THAT is a useful, useful addition, but it has helpfully guided me *away* from fuel flow issues.

[ndutton]

Not really a problem solver in my case but rather making my boat suitable to me. My boat came with a single 12 gallon tank so a Catalina trip 20~25 miles one way (depending on where I go, Catalina Harbor on the backside is more like 30 miles one way) with the very real possibility of very light or no wind put me at 10 gallons consumption round trip if I don't go anywhere else. That's cutting it too close for me with very little reserve so I opted for a second, larger tank instead of carrying jerry jugs or refueling at the island. Once installed I could run off of either tank with a simple Y valve.

Never one to leave well enough alone, with my electric fuel pump it was a very simple task to add the return system with one additional Y valve and a length of 1/4" fuel hose. As I mentioned it gave me easy dry filter purging, the ability to transfer filtered fuel from one tank to the other, easy fuel removal useful in this episode , easy fuel polishing and a shutoff valve immediately ahead of the carburetor (here's why I wanted that valve).

[joe_db]

I’m afraid I don’t understand the problem this is trying to solve. I have no complaints with fuel flow in my single-tank, non-return system - not in operation, when changing water separator filters every few years, or when doing any other maintenance. Maybe this is more for the fancy-pants multiple-fuel-tank types.

You guys enlightened me to the benefits of a fuel pressure gauge many years ago - now THAT is a useful, useful addition, but it has helpfully guided me *away* from fuel flow issues.

My problem was after 2-3 hours running hard in hot weather, my fuel pressure became erratic. First it would drop and bounce back, but as time went by it would spend more time on zero until eventually the engine quit. Backing off the throttle made this worse, so it could happen right at the worst times like coming up a bridge or a dock. This is a classic sign of vapor-lock.
I had a similar issue with a Porsche that was designed for cool German weather, not summer I-95 traffic jams*. Adding a fuel pump in the front of the car where it was much cooler fixed that, the car already had a fuel return but the pump was at the opposite end of the car next to the hot engine.
My friend's old Corvette solved this issue with a pinhole orifice that fed fuel back to the tank.
I plumped up a return line, put a valve in it that is just barely cracked open the tinniest amount, and now I have no issues, I can motor all day and the fuel pressure stays rock-steady

* an emergency cure if you had a cold drink in the car was climbing under it and dumping cold water on the fuel pump, real fun on the side of the beltway