Return Lines

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

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Return Lines

Postby dark_flame221 » Thu Dec 03, 2009 9:58 pm

Hi evrebody ! i know there is aleready a post about a it put it's only for the prupose of one guy..

I would like to how your return line fonction on your conversion... what are the possibilty :
- I saw some that used a 3 way valve that control a return to the diesel and a other return to the vo tank.

- Some other also used a 3 way valve plumbed one return to diesel tank and a other one directly into the sytem at different place in the fuel intake some at the beginning ( before the lift pump ) some before the injection pump.

- And the last, used a 4 way valve, one to the diesel tank, one to the vo tank, one in the fuel system. But i think is the most unreliable way of plumbing the return line, due to is expensive 4 way valve, and because it's have to be electric one, it add chance of system failures, wich obsvioulsy, you try to keep as far away as possible for your sytem, i never saw someone that used a manual one, but could be a great idea




ALSO !!!, i've also tought of an other way of plumbing the return line. i know there is probably some one out there that try it or think about it, but i could find accurate information or someone that tried it.

I know that the main purpose of the return line is to allow the air that is forming from the i dont remember what out the fuel line, BUT what about just taking all the return lines and plumbing them right before the ip ? it's probably to simple, but ! like the system used by SUNWIZARD, when is on vo, there is no place for the air the escape ?! so, i'm waiting for your explication :S

, ALSO ( i've got a lot of also ) in the case that woudnt just work, let's say we take all the return line plumb a T in, plumb one portion right before the lift pump so there is no pression accumulating and take the last protion of the T, plumb to it an hose, leave the other end of it open to the air but put the open head above the higest section of fuel return lines and be shure that no water or debrit can enter in, could that work ? , leave your comment please !! iM waiting impatiently :D
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Postby SunWizard » Fri Dec 04, 2009 9:04 am

Looped is far better on VO than return to tank since you keep the max. heat in there and don't send your heated VO back to tank. If you have an air leak you need to fix it since it will affect performance no matter your plumbing. In normal operation there is no air anywhere.

From this thread:
4 way valve on return. Thoughts?
A 4 way would work, but I have never needed a return to VO tank in the >3 years I have used it. It would provide no benefit since I am always looped on VO. I return to diesel tank to clear any air after a filter change.

You shouldn't tee the loop after your lift pump since that pressurizes the returns which lowers performance and can damage some IPs.

An open hose to air wouldn't work at all, it would just suck in air since there is a slight vacuum before the lift pump.
Last edited by SunWizard on Fri Sep 24, 2010 8:50 am, edited 1 time in total.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Postby dark_flame221 » Fri Dec 04, 2009 11:33 am

ok, but, if we can run vo on a looped sytem with no air trouble, why do we have to plumb a return to the diesel tank ? did somebody already try it ?
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Postby coachgeo » Fri Dec 04, 2009 7:15 pm

dark_flame221 wrote:ok, but, if we can run vo on a looped sytem with no air trouble, why do we have to plumb a return to the diesel tank ? did somebody already try it ?
because it is inevitable that with all the connections... somewhere.. sometime one will leak a micro bit and introduce air. Might not happen for a year or a week.... Having return to tank on the diesel side is just enough to purge those microleaks before they build to a big gulp of air.
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Postby SunWizard » Sat Dec 05, 2009 2:13 pm

dark_flame221 wrote:ok, but, if we can run vo on a looped sytem with no air trouble, why do we have to plumb a return to the diesel tank ? did somebody already try it ?

From my post above:
"I return to diesel tank to clear any air after a filter change."

The return to D2 tank is already there, and you cut that line, and you need to do something with it, so might as well use it since its no extra plumbing.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
SunWizard
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