two-Tank fuel return question - Page 2 - PeachParts Mercedes-Benz Forum

psaboic · #16 07-26-2013, 10:58 AM

Moon,

The banjo bolt on top of the filter that you said needs to be replaced.....are you talking about the big one that holds/tightens the filter cannister, or one of the ones with clear fuel line attached?

psaboic · #17 07-26-2013, 10:59 AM

Grease.....

Thank you, that was the explanation/answer I needed.

moon161 · #18 07-26-2013, 01:01 PM

Good read.

Banjo bolts, 85 300D's and JB Weld - Advice please! - Forums

psaboic · #19 09-13-2013, 10:23 PM

Just an update....We finished the two tank system in the car and it is running great. Only issue we noticed is that lately the hand primer no longer seems to want to work. Actually, it is more like it does not want to depress. It will move about a half an inch and then it is like it is hard as a rock and will not depress any further. Only noticed it when we pulled the in-line filter to check it. Could this have to do with the two tank system or just a coincidence.....

biopete · #20 09-13-2013, 11:21 PM

Quote:

Originally Posted by psaboic

Just an update....We finished the two tank system in the car and it is running great. Only issue we noticed is that lately the hand primer no longer seems to want to work. Actually, it is more like it does not want to depress. It will move about a half an inch and then it is like it is hard as a rock and will not depress any further. Only noticed it when we pulled the in-line filter to check it. Could this have to do with the two tank system or just a coincidence.....

Ideally no. But if your valves are crossed yes. Ie the diesel supply is open but the return valve closed. Maybe turning on key opens it and so the system works except with the key off the valves are out of sync.

I remember not being able to prime my two tank 300d with the primer pump when changing filters and having to disconnect hoses from valves and splicing together to make a more stock config and then I could prime it. It sucked. Also that engine was weak. It was my first Benz and I bought one with bad compression and blowby.

I got an electric lift pump to help. You can get one that lets fuel flow though when it's off so it can just be a primer thing or put on a switch.

biopete · #21 09-13-2013, 11:27 PM

Quote:

Originally Posted by grease lightnig

Fuel Input: diesel goes to the Normally Open Position (NO) the Veg connects to the (NC) Normally Closed Position. The Output going to the IP goes to the Common Side

Fuel Return: The common side connects to the cigar hose that comes from the engine return. The (NO) Normally open side goes to the diesel tank. The (NC) Normally Closed side goes to the Veg Tank.

That is easy enough. But also you need to have two switches or one 3 position electric switch to flush the system so veg does not go into the diesel tank.

To do this with no power to the switch the diesel will go in and return goes to the diesel tank when you flip the switch on then the veg goes into the engine and the return goes to the veg tank. When you flush the Fuel in switch is off and diesel goes into the engine and the return switch is on and goes to the veg tank for a short period of time 15-30 seconds on average. Then both switches are turned off.

When you buy a switch get a 3 position with momentary hold. This means Middle Position is off. Up is on and Down has to be held down for it to work. That way it is really hard to flush all of the diesel into the veg tank. You are only flushing as long as you are holding the switch.

I've never seen a switch like this. Sounds awesome. Where do u get one? I always liked greasecar's 3 way switches and would by those. But they are on off on. Not on off moment.

When you loop the return do you bypass filters and go directly into the ip?

louis4052 · #22 09-20-2013, 12:52 PM

Quote:

Originally Posted by biopete

I've never seen a switch like this. Sounds awesome. Where do u get one? I always liked greasecar's 3 way switches and would by those. But they are on off on. Not on off moment.

I went looking and found this.

http://www.summitracing.com/parts/prf-80402/overview/

A cool idea!

grease lightnig · #23 09-20-2013, 10:25 PM

http://www.allelectronics.com/make-a-store/item/STS-80/DPDT-ON-OFF-ON-MOMENTARY-TOGGLE-SWITCH/1.html

Two of my three two tank cars have the loop behind the filter. MY 84 is return to tank. But my last old Mercedes 300d had it looped in front of the filter.

My grease is really clean. And running multiple passes on the filter is not bad. I change veg fuel filter at every oil change anyway, then it is never an issue.

Jason SVO · #24 10-10-2013, 04:05 PM

Here is a good place for custom rocker switches:

OTRATTW

Jason J
WVO Designs

ZombieResponseUnit · #25 10-16-2013, 07:05 PM

Plurging air from a looped system may be more difficult then returning air to a tank....but running all the way back to the tank is a waste of hose,filters, and valves. My Toyota came from the factory with a looped system and it really just makes sense.

I'm sure others on the forum will disagree with this and call me a luddite, but I opted for 4 ball valves (2 for supply/2 return) instead of 2 three way valves in my Ford b/c I just hate electrical.

grease lightnig · #26 10-18-2013, 08:54 PM

My 2005 CDI has a looped system. It is a well designed system. When I change the fuel filter about every 5000 miles with oil changes, I put a pail before the fuel switching valve and turn on the electric veg pump and it pumps grease and air out of the system, then reattach the hose. Mine has a 60 plus psi fuel pump. The loop is behind the veg fuel filter and fuel pump.

Mine also has three valves for fuel switching. One for fuel in and two for fuel return that way when I flip the switch on (they are all electric) the diesel fuel pump just returns to the diesel tank. When I flush the diesel the diesel goes in and the veg return switch is still on to keep from pushing veg in the lines into the diesel tank.

The loop eliminates a lot of hose and fittings for sure. I find it is important to use good fittings. I use push lock flare fittings and Pex line that I heat up and force the fittings into. This makes a great seal and no air gets into the system. And the price difference is negligible because I do not have any hose clamps in my system.

jltcasper3 · #27 10-31-2013, 10:02 PM

For 2 tank VO system schematics see link below, click on install manual and then go to pages 16 for a 2 valve system and page 17 for a 3 valve (controlled loop system) This may clarifie some things for some people. This is thanks to frybrid.

Frybrid Vegetable Oil Fuel Systems -- Manuals