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Old 06-05-2008, 09:46 AM
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Join Date: Jan 2007
Posts: 271
Modify banjo bolt to keep diesel from circulating back to the tank?

Hello all,

I converted one of my cars to veggie oil a long time ago. Fuel was cheap then and so I stopped using my conversion, too much of a pain in the ass and didnt want to damage expensive components on the car.

Now with diesel so expensive, I either need to sell my car or re convert - so I am going to re convert.

I need to figure out how to keep the overflow fuel from being pumped back into the tank. I want it to recirculate so the heated fuel stays in the engine bay.

I have been told there is a way to modify the banjo bolt to make this happen, so the fuel keeps going in circles and never goes back to the tank. Can anyone tell me how this is done?

I understand the problems that can come up if air gets into the system, and am prepaired to deal with that

Thanks for any help.

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Old 06-05-2008, 10:03 AM
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Gotta another one...
Join Date: Jun 2005
Location: NE Ohio
Posts: 1,685
I think you just take the return, and loop it into the supply hose (you have to tee the supply). I think you need some sort of bleeder in there to bleed off air after so many miles (else air gets stuck in the lines).
1989 300E 144K
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Old 06-05-2008, 10:37 AM
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Ya, I know I could throw a T in there, but then I would for one need to find a T (which I have not been able to find) and also it would be much easier to modify the banjo bolt. Then when I do need to bleed the air out, I can set it back to normal and use the standard primer pump.
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Old 06-05-2008, 10:40 AM
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Location: Old Town, Fl
Posts: 350
You need to loop the return to the suction side of the lift pump. Looping to the output (pressure side) over rides the internal pressure regulator in the IP. There needs to be a pressure differential between the input & return side of the IP.
Plugging the banjo return will increase the temp of the diesel fuel when you're not running on WVO. The return to the tank is to keep the temp of the fuel down to maintain it's lubricity for the IP. It would be best to use a solenoid valve to redirect the return for each fuel.
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85 300TD 282K
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Old 06-05-2008, 12:00 PM
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Ya I would put something like a fuel selector, but im doing a single tank system, veggie oil going right into the main tank, and ony veggie oil. I live in a hot climate so I can get away with it
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Old 06-05-2008, 12:36 PM
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Join Date: Mar 2006
Location: minnesota,hey.
Posts: 1,841
you need to replace the bolt w/ a solid one, or weld it shut, or JB weld it. if you do not do this, when u switch to veg it will return veg into your diesel tank.

you also need to loop your return. try a 3/8 PEX( a type of plumbing) T from the local big box home store.
1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.
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Old 06-05-2008, 01:21 PM
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Join Date: Jun 2006
Location: NY
Posts: 710
If you are doing a single tank (which I don't really reccomend), just put a 5/16" T between the inline filter and the lift pump. Cut the line between the Ip outlet pressure regulator and the filter banjo about 3/4" from the banjo nipple. Cap the stub on the banjo nipple. Connect a 5/16" fuel line from the IP outlet to the T.

This will return the IP overflow back to the inlet of the lift pump but still allow the injector overflow (less than a pint/day) and the air from the filter to return to the tank. A small amount of fuel will also go along with the air from the filter but most of the fuel will recirculate in the loop.

Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
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