Greasecar giving me pains... '80 300D - PeachParts Mercedes-Benz Forum

driad_98 · #1 07-12-2004, 09:39 PM

Alright, so I've got the overflow from the fuel filter housing going through a valve. In 'normal' position, it gets sent right back to the diesel tank, but in 'grease mode' it loops back into the intake line. This is supposed to keep the oil up to temp. (I have triple bypass hosing in place, so the oil's heated all the way from the coolant-heated tank, along the underbody, and into the engine compartment. )

I've got clear lines in place, and through them I see that the overflow from the banjo fitting has bubbles in it. These bubbles in normal mode just go back to the tank, but in grease mode they accumulate and choke out the engine. I've just replaced the banjo bolt with a 12mm/1.5/20mm bolt. I've also torqued down the filter bolt, and both 'in' and 'out' banjo fittings.

Questions:
If one of the overflow (black, braided and replaced less than a year ago) lines was compromised, wouldn't it be wet?

Are there seals on the IP that could allow air into the system? Is it possible for froth to make it through the injector-sites and back out through the overflow? I'm just about out of ideas... which brings me to... running the grease overflow back to the tank in the trunk. Anyone wanna warn me off of that?

Thanks for your attention, guys... I'm about at wits end. Cheers!

Ash

rwthomas1 · #2 07-12-2004, 11:01 PM

Everything I've read indicates that you can run the grease back to the grease tank like a standard system without issue. Supposedly you may have problems with the grease not getting hot enough but I doubt it given your location. I am planning a conversion and I will run a return line. To me a fuel system should operate as designed. RT

coachgeo · #3 07-13-2004, 12:13 AM

ok...... here we go again. lol.

If I read you right you are using ONLY the OEM fuel filter and NOT a second fuel filter. When your switch is thrown for WVO you have the "complete" overflow coming out of the banjo bolt ontop of the filter looping back to the IP intake (fuel supply) right?

If you do this on an MB this wont work! You see the banjo "bolt" ontop of of the fuel filter is actually an air bleed for the complete fuel system. What it does is to bleed air (and a little fuel) from inside the fuel filter up thru the bolt and into the banjo "housing" atop the filter. This air mixes with the return fuel from the IP and the Injectors and heads off to the tank thru the cigar hose and and then the metal return line. In your present arrangement;
when you are switched to the fuel return loop mode this air just gets fed into the IP.

Solution 1: take out the banjo bolt from the filter. Fill the hole in the "bottom" center of the bolt with JB weld. Let it dry and replace the bolt. Tada... no more air bleeds up thru the filter. Now you have to plumb in a way to purge the system of air on occasion.

Solution 2: Harder to describe than it is to do the work. IMHO this is the way to go. Tony West of Oz will straighten me out if I explain it wrong. THANX for the idea Tony.

a: Take off the banjo bolt "housing" from the IP fuel supply.

B. Take off the banjo bolt return "housing" off the Fuel filter. (it has three ports; one small and two larger)

C. Put the fuel filter banjo "housing" onto the IP Supply banjo "bolt ". Dont swap bolts. and put the IP banjo housing onto the fuel filter's Banjo bolt.

You have now swapped banjo housings but not the bolts.

D. Plumb a single line off the port that is now ontop of the fuel filter to a brass "T" The straight thru leg of this plumb to the cigar hose return line. You will use the last leg of the "T" in step H.

You now have kept intact the air bleed system MB intended. YES this always returns "a little bit" of fuel (and air) to the diesel tank including when running WVO. Dont worry, a Little WVO in your diesel won't be a problem less you live in the GREAT WHITE NORTH and this may not be an issue either with planning.

E. Plumb the injector return line to the smaller port on the Banjo housing that is now on the IP fuel supply. This allways loops the little bit of fuel from the injectors. no biggy.

F. Plumb the IP return line thru a polick valve switch. One side of valve (powered side) is plumbed to the same banjo housing as the injector return on the IP. (when powerd this is your fuel return loop)

G. Plumb the incomming fuel from the filter to the IP via the remaing port on the banjo housing that is now on the IP. (remember, it now has three ports; one small and two larger)

H. The unpowered side of the switch is plumbed to a "T" on the return line from the filter. This is so the fuel can also go to the fuel tank thru the cigar hose. (Switch is set here when using diesel )

On the IP fuel supply banjo you have now entering this three ported banjo: 1. returning fuel from the injectors. 2. The fuel from the fuel filter and; when switched, 3. the returning fuel from the IP (fuel return loop)

Confused yet? If you use a second filter for WVO the plumbing is simular.

driad_98 · #4 07-13-2004, 01:50 AM

That's comforting. Thanks. Still I'm wondering where the air's coming from. If there was a leak in the fitting for the hard fuel line, at either end, it'd spray fuel, right, not suck air? So the air has to be in the mix pre-ip, right? The IP spools up the pressure alot, right? Hmmmm... Working... Working...

driad_98 · #5 07-13-2004, 01:54 AM

Woof, I'll be reading that thoroughly tomarrow, Geo, my GF's here and antsy.

Thanks a ton! I do have a secondary/grease filter, but your advise still makes sense. Trouble is, I replaced the banjo on the filter housing with a solid bolt today, and I still have froth coming through the overflow. Looks like it's coming from the injector-overflow-daisychain thing, no the IP overflow. Does that suggest anything to you? Thanks a ton for taking the time!

Ash

Cazzzidy · #6 07-13-2004, 04:43 AM

Running a fuel loop eases strain on IP and lift pump by providing warm, easy to flow oil. It also makes warm up and shutdown switchovers shorter, because you can start on a blend in your loop instead of totally purging wvo.

Apparently the 6 port solenoids are more reliable than the 3 ports though... an added benifet of running return lines.

Sorry, no advice about the bubbles.

JamesStein · #7 07-13-2004, 09:39 AM

This is how I setup my system.

http://biodiesel.infopop.cc/eve/ubb.x?a=tpc&s=447609751&f=444600361&m=813100992

I have no problems with air in the lines. And yes this way diesel gets into the WVO and WVO gets into the disel when I switch over. Once every couple of months I drive my main tank empty and refill it 1/2 way with diesel.

coachgeo · #8 07-13-2004, 10:13 AM

Quote:

Originally posted by Cazzzidy
....Apparently the 6 port solenoids are more reliable than the 3 ports though... an added benifet of running return lines.

Sorry, no advice about the bubbles.

actually that may be the source of your troubles. Take out the switch over temporatily make iti a full time loop. See if that stops your bubbles. If so then you valve is leaking air.

Another source may be your pump. The pump/handpump combination on the side of your engine may be your leaker. Check the archives here about that.

As to an earlier statement. No you dont get a fuel spray out of a leaking fuel line. On Injected gas engines the fuel pump is in the tank and it pushes fuel thru the hose and as well as out any leak spots. On carb. engines the fuel is sucked from the tank to the pump and then is pushed everywhere else.

On a diesel the fuel is sucked from the tank via a pump up in the engine department. There for a leak in a fuel line sucks air into the system. With the engine off some fuel "might" find its way to drip out of the leak.

TonyFromWestOz · #9 07-13-2004, 10:21 AM

I have posted my looped return 2 tank WVO conversion on the Infopp forum
This is an interim configuration while waiting for my 6 port Pollack valve to arrive (~10 weeks by surface freight)
When I install it, I will be using a looped WVO, returned main tank (WVO:Biodiesel blend)
I am using a 5 psi fuel pump at the tank. At idle, once warmed up, I get ~4 psi at IP inlet. and 5-6 psi when engine is off. I plan to use a 15psi Holley Blue when it arrives (in 4 weeks). This is to overcome the pressure drop when using unheated oils in winter (~10 psi drop from pump thru fuel lines, heater and filter).

TwitchKitty · #10 07-13-2004, 12:40 PM

Quote:

I am using a 5 psi fuel pump at the tank. At idle, once warmed up, I get ~4 psi at IP inlet. and 5-6 psi when engine is off. I plan to use a 15psi Holley Blue when it arrives (in 4 weeks). This is to overcome the pressure drop when using unheated oils in winter (~10 psi drop from pump thru fuel lines, heater and filter).

Would there be any problem with running an electric boost pump back at the fuel tank on the original system?

driad_98 · #11 07-13-2004, 01:59 PM

The bubbles appear while on diesel too, though at a much decreased rate.

The overflow lines get wet when they're leaky, I've seen it before... they're pressurized, not under vacuum, right?

I was talking about the hard fuel lines from the IP to the injectors. If those were compromised, they'd also spray, right? A la drip test.

Hmm.. The hand pump works great, but I guess it could be leaking... in fact, I got diesel on my glove when priming the system... though that's normal, now isn't it?

It's so frustrating, I want to run the loop, but if I can't find this leak, I'll run a return line. Will an air leak like this sap power?

Oh, answer me this...
If there's air in the final (clear) fuel line TO the IP, will the air get run through the combustion process, or will it carry on through the overflow lines? I've always been under the impression that it'd go through the injectors and thus 'self prime' to a degree... if this is an incorrect assumption, things are different. Anyone know? Thanks!

Ash

driad_98 · #12 07-13-2004, 05:00 PM

Ok, the leak got worse and thus showed itself. One of the clear lines from tthe filter to the IP sprung a pinhole. I got some tubing that fits and claims chemical resistance from OSH. The new parts from MBZ are expensive... or not really, since they come with the hardware, but all I need's new tubing.

I'll let you know if this fix fixes the problem. Thanks a ton, all.

Ahs

djugurba · #13 07-14-2004, 01:14 AM

I'm still fighting wierd little leaks here/there as well on the SDL. I'm currently of the opinion that I need to go back and locktite all of the brass t/barb connectors because if the car sits for a day or two enough air gets in the line that I've got to crank it to purge (that's how you purge the 603). then it's fine- runs great. also have a smallish little drip of coolant at one of these brass t/barbs as well, so that is extra ammo for that idea. if I'm lazy, can I just jbweld them while they are in place so I don't have to rip everything out? please???

cheers,
Kevin

TonyFromWestOz · #14 07-14-2004, 09:03 AM

Quote:

Originally posted by TwitchKitty
Would there be any problem with running an electric boost pump back at the fuel tank on the original system?

there should be no problem, providing you don't go past the mechanicla lift pump's output of 15psi.

driad_98 · #15 07-14-2004, 03:40 PM

So the leak in the filter to IP line wasn't the sum of the problem. I ended up running a return line to the grease tank, and in my climate, with the quality of oil I get, I'm quite content to call it done.

Now, I think I need new shocks. Any reason not to get something other than Bilsteins?

On an unrelated note, I'm looking at picking up a (yes, slow, I know) 240D from '82. Looks really straight and clean, only a few flaws... 260K on the non-working clock, super clean underbody and engine (claims no cleaning done), manual tranny, manual windows, sunroof works, central locks work... black with 16" accessory wheels... Hopefully I'll be able to get it for $1200... opinions?

Another related note, does anyone have a W123 brake booster to sell me? Thanks!

Ash