You are using a 2 tank WVO system, right?

If so, you had to change the routing of the lines a bit - basically the lift pump would now be last thing in line before the IP, whereas the factory set up puts LP 1st from tank and pressurizes fuel thru main filter, preheater, and on to IP.

What all this means is that when running on D2, you are pulling fuel all the way thru system. For some reason, I have had to keep at least 1/4 tank of D2 or it will stall and be a ***** to restart. If I keep it over 1/4 tank D2, the dino runs flawlessly. So, Ive just treated the D2 fuel gage as 1/4 means 0. Hell I only fill up once every 4-6 weeks anyways.
I suspected this was because the fuel system being under vacuum is less efficient than pressurized. And it relied on a bit of pressure head from D2 tank to get job done (ie, at least 1/4 tank).

But hell, maybe the filter screen is clogged and thats causing all this. How hard is it to pull it? (87 300D).

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Paul
Benz-less
I need an SDL !

Paul, you are right about the two-tank setup, rerouting so the lift pump is last instead of first, etc. And this could explain it, except that it is only a recent problem, and I've been running in this formation for almost 20 months with no problems, fuel gauge goes down to the "R" mark before running out. Only in the last month or two has the car run out at the 1/4 tank mark.

One thought is that my lift pump is weakened, though I'm not 100% sure why it would be weaker at 1/4 tank than at any other level, though lessened pressure (like you said) might be part of it. Another reason I suspect the LP is that it's been running rougher on WVO for a while, perhaps the higher viscosity is a problem (I only run it hot, don't worry). It's only really noticeable at idle, and when restarting the car after a brief shutdown on WVO. At that point the car shakes roughly and acts fuel starved for a while. This doesn't happen when switching after warming up on diesel first, only after making a brief stop on WVO, then restarting. Even after only 10 minutes (fuel still plenty hot) it complains.

I don't know how bad it'll be to pull the tank strainer, but next time my tank is really low I'm going to try it, just to see. Since there's no way to verify whether my send/return lines are on correctly by the suggestions made above, I won't be doing that just yet. If the strainer is clean (relatively), it might be the LP. Heck, even if the strainer is dirty, it might be the LP, but I'll start at the tank strainer first.

Any other suggestions are encouraged and appreciated

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JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

We may have the same issue (on 2 different models).

I seem to recall when I 1st did the switch to WVO, the car could run down to nearly empty on D2 tank without problems, but now, like your car, it has trouble. From what I understand, the LP's are bulletproof, so Im really suspecting clogged D2 tank screen at this point.

Ive also got some rough idle problems cold.

Well, if it is the LP good news for you and bad for me. Yours is cheap, mine is $$.

Like others have said, having vac gages rigged into plumbing is invaluable. Its only another few hose clamps and couple MORE feet of wiring Stick 1 before and 1 after wvo filter housing, and you will not only be able to see system vac for knowing if LP is working, but you will also see filter condition (ie, too much delta V and you have clogged filter). You could also rig in a 3rd vac sensor for the D2 lines to monitor that side as well.

Im confused as to why you dont know if your system is routed correctly. All you need to identify would be the hard metal intake and return lines (on the frame rail).

On the D2 side of things, from in the metal fuel intake line, you should be going to main filter, then to intake solenoid valve, then to LP, then to IP (no need for the prefilter, since that was only to protect LP - but it doesnt hurt to keep it). Your D2 return should go to the main filter housing, but the banjo bolt should be plugged up with JB weld, or replaced with solid bolt. Then to the return solenoid, then back to hard metal D2 return line. -- this is for cars with no D2 preheater (I believe the 123's didnt get those).

On the WVO side, from the wvo tank to the wvo filter housing, then to final heat exchanger, then to intake solenoid valve, then its same line as the D2 side to LP and onto IP. Return line is same line as D2 - to main filter housing (with banjo bolt plugged). Then to return solenoid, then back to WVO tank.

Some also wire in a 3rd solenoid valve for purge, and/or also loop the return back to wvo filter housing. These 2 are optional, but I highly recommend looping return line back to wvo filter housing, with a small hand actuated valve that allows for either looped return, or return back to wvo tank for manual purges (I use the looped return and send back to wvo tank only immediately after changing wvo filter as it helps send air bubbles back to wvo tank instead of back to injectors).

Hope any of this helps, its really a quite simple system on these cars, especially OM617 engines. Just trace lines and ensure its hooked up correctly before troubleshooting.

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Paul
Benz-less
I need an SDL !

the in tank strainer is plugged! Been there done that,take it out and clean it. Don

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Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles

any quick solutions to plugging the tank while you clean the screen?

...instead of draining the tank..

On the wagons, there are no fuel lines running from the strainer, easy removal.

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Boy that would be a good trick. I'd like to know if there is a way to do that. I ran my tank down as low as I dared and then loosened the strainer with a 5-gal bucket under it (a quick way to do that is let the car run while purging). The strainer was in there pretty friggin tight on mine. I made a hex key to fit it with a bolt and nut and jb weld...I tried locking two nuts together and they just loosened.

Its easy to check the strainer from above by taking out the tank sender. Run the tank down, take out the sender and look in the hole with a flashlight. Then you can clean the sender

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Roll the car over.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

if you saw the hill I park on.. that is almost tempting.

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I have the right size hex for that.. shouldnt be an issue.

That is great advise.. I am at 1/4 right now waiting for the right opportunity to jump on this. I will definitely try that. thanks

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jt20,

You have a wagon, I take it, from your sig. line. I did some poking around on here and the hex size is 22mm, if I remember correctly. Is that true in your experience? Anyone?

If I can borrow a 22mm hex from someone I know I'll do this next time my tank is low.

JBG

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JBG
1985 TD wagon, 228k
running on grease since 3.07
AUSTIN, TEXAS

Has anyone replaced in tank strainer on 87 300D ? If so, how ?

This problem is really pissing me off. I swear I better not kill another starter motor! My knuckles are still bruised from 1st time I had to replace it.

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Paul
Benz-less
I need an SDL !