Fuel return modifications - Page 2 - PeachParts Mercedes-Benz Forum

coachgeo · #16 08-15-2003, 10:48 PM

Quote:

Originally posted by BoostnBenz
....
What sort of suggestions are you angling for? Your model 1 appears right on to me. You'll just have a hose whatever size OD your fittings it Ting into the current 7mm feed fuel hose for your WVO's return. The diesel return is automatically correct because of your setup.

well..... the biggest quandry I was having was how can I plumb all this without slowing the returning fuel down below OEM designs. I knew this would create back pressure and worried this may cause problems. I wanted assitance in choosing which of my designs would work the best with this in mind.

Another headache that I saw creeping up was the problems posed with the small size injector return line. Especially when it comes to "T"ing this line to the larger IP return line.

I had hopped to have a lot of this hashed out from info from here and other boards in advance; prior to getting in there and doing the actual plumbing. Oh well..... Time lines of reality on the boards and when I needed to do the hands on work just didnt match up this time. Thanks for asking how you might could help me.

Soooo..... anyway.... yesturday as I started to plumb away I realized.... OH SHIATTTTT. Neither one of the actual designs I posted here would work because my 12v fuel pump will push fuel from the tank UP my return line that is "T"ed into the incomming fuel line from my pump. The pressure of the fuel pump would over power the pressure of the fuel comming in from the return lines thus it would back flow up the return lines.

I had two choises.... a 15 dollar check valve or a 4 dollar gas pre filter with a built in air bleed. Guess which one I took

Also this filter made installation easier just cause it all the plumbing ended up in more accessable areas. Another words..... I completely skipped feeding the WVO return loop back into the MB fuel filter. I ended up using the gas fuel filter w/bleed instead. I put this gizmo in the typical fuel return loop and fed the bleed to the Injector return port on the Banjo. Most the fuel goes on to a "T" in the fuel feed line from the filter to the IP. Being able to bleed air out of the returning WVO fuel was the intent of my designs from the get go.

When I select with the valve to run on just diesel the two returns "T"ed together feeds into the port on the banjo that orginally was just for the IP return.

Now that sounds simple... buttttttt....

You touched lighty above on the issue of getting return lines to "T" together. In reality doing this was a PITA. The fact that the banjo return bolt atop of the MB filter has two different hose sizesposed a big problem that I searched High and Low to solve. "T"ing the two sized together was a nightmare. They are no local supplies of quality nipples, reducers, etc. available for use with hose as small as the injector fuel return line. I ended up using a universal vacuum hose "T" that had muliti sizes on all three ports. I also used a piece cut off of one of these to splice a 1/4" line to the small injector line (apx. 1/8") so it could connect to the injector retrun port of the the banjo. I'm not real happy about this but I had no choice. Also hose clamps are not really made to work with line that small.

Oh welll...... I managed.. and TADAAAAAA.

IM WVO POWERD NOW BABBBY

BoostnBenz · #17 08-16-2003, 02:09 AM

Sounds great, congrats, I'm still debating which route to go. I guess I'll need to secure a supply first of all. If I decide to go the WVO route I now know how to hook it up, thanks.

I'm not sure if brass is impervious to the fuels but you can always get one of those brass blocks which can be either for brake systems or used as Ts. You can then pick which size nipple goes into each location. The plastic will probably be fine, but it'd be nice to have some clamps on there for piece of mind. There are two ways to do it, the way I don't care for is using small zip ties. The way I think would work a lot better would be to find some squeeze clamps for that size. My talon uses a lot of those, especially for that small of a line.

Well one problem I see with that if I understood it right was that you used a filter on the WVO only side to manifold them together, well couldn't that clog up if it got cold? Then without diesel running through it or heated fuel making it to it how would it clear? Maybe I'm being to critical.

coachgeo · #18 08-16-2003, 08:52 AM

Quote:

Originally posted by BoostnBenz
...I'm not sure if brass is impervious to the fuels but you can always get one of those brass blocks which can be either for brake systems or used as Ts. You can then pick which size nipple goes into each location.

They didnt go down to a small enough nipple (1/8")where I looked.

Quote:

it'd be nice to have some clamps on there for piece of mind. There are two ways to do it, the way I don't care for is using small zip ties.

did that in two places.

Quote:

The way I think would work a lot better would be to find some squeeze clamps for that size....

thats the item I returned to Advanced Auto. Their smallest ones also were not small enough. They excerted no pressure on the hose at all.

Quote:

Well one problem I see with that if I understood it right was that you used a filter on the WVO only side to manifold them together,

No I did it to bleed any air that may be comming out of either return. They are manifolded together via a "T" prior to the valve

Quote:

well couldn't that clog up if it got cold? Then without diesel running through it or heated fuel making it to it how would it clear? Maybe I'm being to critical.

nah that is good question. Yeah it would if I did not purge. This valve would be switched to diesel "after" sending diesel thru this path, though (purging) . That is further into phaze two though. Not to much an issue right now cause it is summer and cause I am using a blend of 10% gasloline too. thanks for you input

BenzDieselTuner · #19 04-07-2013, 11:45 AM

ok, i'v spent about an hour searching the internet, and i understand the concept of the fuel return, but i still cant find enough info to figure out if my temporary idea will work.....in my head it makes sense.....what do you guys think ?

fuel return goes into the cigar hose (or regular hose), then being routed to the metal return to the tank.....i am thinking, since my electric boost pump is still on front for now, connected to the fuel flow as it comes in from the steel line to the tank, before all prefilters and heat exchanger, why couldnt i take a T, and plumb the return as follows : put a T on the feed hose coming from the tank, before my electric pump and prefilters and FPHE.....take the return hose (cigar hose), and plumb it into this T.....at the point of the T, fuel is being sucked towards the electric pump and lift pump.....the fuel coming out of the return line is under slight pulsating pressure, so if anything, it would help push fuel through the pumps filters and the whole works.....because of the flow/suction going towards the motor from this T, i would think that it wouldnt backflow down the line back to the tank, and i would get fuel still to the fuel system, maybe even at an increased pressure.....

am i wrong for some reason ? or have i correctly understood the concept of the fuel flow / return system ??

BenzDieselTuner · #20 04-08-2013, 09:51 AM

Quote:

Originally Posted by BenzDieselTuner

ok, i'v spent about an hour searching the internet, and i understand the concept of the fuel return, but i still cant find enough info to figure out if my temporary idea will work.....in my head it makes sense.....what do you guys think ?

fuel return goes into the cigar hose (or regular hose), then being routed to the metal return to the tank.....i am thinking, since my electric boost pump is still on front for now, connected to the fuel flow as it comes in from the steel line to the tank, before all prefilters and heat exchanger, why couldnt i take a T, and plumb the return as follows : put a T on the feed hose coming from the tank, before my electric pump and prefilters and FPHE.....take the return hose (cigar hose), and plumb it into this T.....at the point of the T, fuel is being sucked towards the electric pump and lift pump.....the fuel coming out of the return line is under slight pulsating pressure, so if anything, it would help push fuel through the pumps filters and the whole works.....because of the flow/suction going towards the motor from this T, i would think that it wouldnt backflow down the line back to the tank, and i would get fuel still to the fuel system, maybe even at an increased pressure.....

am i wrong for some reason ? or have i correctly understood the concept of the fuel flow / return system ??

no answers huh ? well such a tee is cheap, so i will go and get one and hook it up like i said, and i will report the results later on....

Jimec3 · #21 04-08-2013, 10:17 AM

It sounds to me like you have it WAY over-complicated

Mercedes 1987 300D 2-tank setup diagram - Topic

maybe my understanding of what you are saying is off....

As for the Biodiesel discusion. The costs goes down when you begin adding other vehicles to the fleet. There is no need to setup and maintain multiple WVO systems with filters etc. .40/gal seems a little adventurous but $1/gal would be possible depending on how efficient you were.
I invested 200 in equipemt (bought used) and I spend 1 hour per 13 gallons of biodiesel at the worst and 1/25 at best.

BenzDieselTuner · #22 04-08-2013, 10:29 AM

what i was thinking of doing, it is routed just like that on the one diagram on the link u posted.....fuel return can be looped into the fuel input line, before the lift pump (and in my case also the FPHE and electric auxilary pump)

Jimec3 · #23 04-08-2013, 10:33 AM

If it were me I would leave the stock return loop between the IP/nozzles and the stock filter alone. Any problems you might have (failed fuel pump, leaky valve etc) would then be contained to the WVO system allowing you to drive the car as you normally would under diesel power. My 2cents

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