Last injector return line with a plug is normal.
I'd replace the filters first. Then try the bottle of fuel in the engine compartment. Put two clear lines in a 16 ox pop bottle, one attached to the return line on the canister fuel filter assembly and the other to the input of the small plastic filter. Fuel should get sucked from the bottle and recirculated back into it. A 16 oz (or so) bottle fits well between the inner fender and a hose on my TD. You could drive it around like that to test it if yours fits the same way.
The return line is the 'fat' cigar hose coming off the canister filter assembly. The incoming line goes directly to the small plastic filter. You'll need some additional hose if you want to switch them, or perhaps you can remove the two hoses where they attach to metal lines.
It might work to blow compressed air through the incoming line back through the tank. It would be even better to extend it, put your mouth on the hose and blow through it to see how much resistance you get. I was having problems in a 72 Chevy wagon dying out and found an additional fuel filter someone had installed in the line by blowing backwards through the fuel line and getting a lot of resistance.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I would start with a fuel filter change. Then go for a drive see if the problem goes away or not. If not then try switching the lines to see if the tank screen is clogged.

The last injector should have a short line with a plug on it. So don't worry about that, but I would change the rest of the lines that are vac lines. Problems probably won't arise instantly but I would find some new fuel line to replace the vac lines with.

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The bottle under the hood is another good idea to diagnose the fuel delivery up to the IP. Also, make sure the return hoses between injectors are in good shape and that they are the braided type. I tried to cheap out and use regular fuel line on those and they leaked like crazy. Good luck.

I agree with the fuel filter/tank screen diagnosis. The filters my look fine but could still be plugged. The behavior of the oil gauge is normal, as is the small amount of oil in the turbo. The smoke when starting is likely the valve stem seals. Mine used to smoke when started...now it smokes all the time. Those seals are next up on my repair radar.

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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

Please don't forget to let us know how things are going with getting your Benz back on the road. I've always thought that the ONLY thing wrong with this forum is that the folks asking for advice don't let anyone else know what finally works. That kind of info is priceless. Thanks and good luck with your trip.

well, i'm still tryin'! replaced the primary filter, and upon inspection, the old one did spit out bit of sludge. replacement didn't fix the problem though, and couldn't locate a secondary filter over the weekend, so am going to pick one up as soon as the import shop opens this morning.

did try switching the send and return lines, to no avail. actually, the car didn't even start when i attempted that. tried blowing with my mouth back through the send line and couldn't get any movement or force any air up there....

linkage all seems good, and there's no carpet bunched up under the accelerator ....
i noticed that two of the fuel tank vent hoses that go to the little auxillary tank near the spare tire are loose and hanging, as that tank's plastic nipples have broken...but i don't imagine that would be a huge problem, would it?

my plan is to try this next fuel filter, and if that doesnt work, take it to a shop here in houston and try to get them to do the in-tank screen this afternoon. I'm hoping and praying that it IS something simple like y'all have suggested so i can get BACK on the ROAD.

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-lee
'83 300CDT (286k)

former proud owner of:
'85 mercedes euro 300TD
'80 mercedes 300TD
'77 mercedes 280e
'80 mercedes euro 250
'82 mercedes euro 250

my .02 is that you've got a plugged tank screen, vent, or both..
Let us know what finally solves the problem..

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'79 300D, Ivory "Gunther" ......going
'81 300SD, Metallic Blue Silver, The Grey Ghost.....going
'87 300D Turbo ...gone
'05 CDI.... gone

If the vent is obstructed, removing the fuel cap should restore normal performance, at least temporarily.

A pop bottle some vinyl hose and a quart of diesel could confirm a problem with the tank quickly. Plumb it in to the system and see how it runs.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Also clean the banjo bolt that contains the line that runs to the turbo switchover valve, and then on to the ALDA. My turbo switch over valve was stuck closed, and the banjo bolt was patially plugged w/soot.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

If either or both fuel filters are clogged you can experience no power. So make sure you eventually replace both, especially since one was gooy. Also try the fuel lines in the bottle trick to rule in or out the tank strainer.
Follow the instructions that Diesel Giant gives on his DIY Diesel Purge. Hook the bottle up just like he does in the write-up, but you can just use some clean diesel. This will tell you if the tank strainer is clogged or not.

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WELL.
it's been a long couple of weeks, but I'm finally home from my Texas-to-Oregon road trip. i'll be posting another question here in a minute on the comedy of errors and crappy luck plagueing my trip, but, first things first:

sorry i haven't posted an earlier resolution reply, but i've been on the road and internet restricted.

as far as THIS post and its resoulution is concerned:

it baffled me because of the ORDER in which all this bad running/lack of power stuff all happened, but, long story short: both fuel filters were clogged AND the primer pump was bad AND the fuel gauge was faulty.
thanks so much for all your help on this one. got me from Houston to northern New Mexico, before experiencing any other trouble

__________________
-lee
'83 300CDT (286k)

former proud owner of:
'85 mercedes euro 300TD
'80 mercedes 300TD
'77 mercedes 280e
'80 mercedes euro 250
'82 mercedes euro 250