I drive a 82 300sd on veggie oil. I have a sytem that has a pump in the rear with a prefilter and heater. Under the hood, I use a large filter/water block/heater with a smaller final filter. I experienced similar problems as yours until I bought a larger final filter with more capacity. That was my culprit because it seemed to restrict the fuel at that point in the system. I haven't had any issues in 30,000 miles since getting the larger final filter. I am no expert by any means, but air & fuel restriction, clogged up filters would seem to cause your problem. Keep going.

__________________
1982 300
1984 300cd
2005 GMC Yukon
1967 GTO Hardtop x 2
1967 GTO Conv.
2002 Harley Softail Classic

I have the same problem (only running pump diesel and little different body then the W123)

Help Jeep-OM617turbo swap intermitten power??

I have pulled my hair completely out and my beard is now turning grey..

Let me know if you find it (seems to be only after x amount of time and engine starts and idles fine)

Thanks for all the replies and I'm truly sorry for anyone experiencing something like this. I feel like we've replaced all the parts on the car except the one that is causing the fuel starvation symptoms.
I put some pump diesel in our 1985 300D yesterday and it ran ok the rest of the 20 miles home after dying on the way into the gas station from the same sputtering as I've previously described.
We looked back last night and realized that we had not tried running the car with the gas tank full since these issues have surfaced. We're trying that today.
In addition, I started the car last night in the dark and held a flashlight to the clear inline filter before the injection pump while I revved the engine. To my surprise (and hopefully a specific diagnosis) there are obvious bubbles that go through the filter when I rev the engine fairly high. They are probably only about 2-3mm in diameter but I'm sure at sustained high speeds or hills these could build up and cause my injectors to vapor lock. Is that a fair analysis?? Like the previous post, my hair is about to be gone as well except I don't have a beard to turn gray.
Thanks to anyone who donates their knowledge.
Brandon Oswald
Pensaocola, FL
1979 300D "Red"
1985 300D Turbo "Blue"

That will do it

__________________
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

I've been running WVO for a couple of summers now and have never experienced this problem... until last week.

Starting a couple weeks ago, my in-line filter started to clog up almost immediately with this black gummy stuff. All was fine on my Thursday night drive home, but the car wouldn't start Friday morning. I surmised that the screen on the tank was probably clogged. Ever since I bought the car several years ago, when starting to get low on fuel, the car always start to stall after making any sharp right hand turn. I figured this was probably do to a partially obstructed screen that caused fuel unporting of the fuel pickup on the turns.

Over the weekend I removed the tank and found the screen all covered with this black rubbery stuff. Gunk and a small scrub brush would not remove it, but Greased Lightning did. I rinsed out the tank and reinstalled everything. The tank drained fine now but I still had a problem with the lift pump. It would not draw anything. I happen to have a spare lift pump, so I replaced it and verified that I could now draw fuel to the secondary filter.

At this point the car acts like yours does. I have good power sometimes, but it sometimes acts fuel starved. I think I still have some of that crap clogging the injection pump/lines/injectors. I gone to the parts store and picked up some Diesel911 and emptied it into the tank as it was the best stuff they have. No change yet. I have to drive the surface streets to get to work now.

What else can I try to clean the IP out?

BTW: It's normal to see air in the first filter.

Attached Thumbnails

 

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

I too was having fuel delivery problems and bubbles in the line coming out of the lift pump. I replaced all lines under the hood with Viton and I pulled the line coming from the tank to the primary fuel filter and normally fuel should be drooling out. I had no fuel draining out of the hose. With compressed air, I blew backwards into the hose from the tank with the fuel cap off and cleared the line. I primed the system and removed the line from the tank again and fuel came out at a good clip. I took it for a ride and it ran like a scalded dog... After about an hour of driving it started acting up again It appears that the tank screen it full of crap again, since fuel won't drool out of the line from the tank. So tomorrow, I am replacing all the tank hoses, removing and flushing the tank and tank screen. I am confident this will cure my ailing 300 CD.

The alt fuel supply test is very important. I would also try the next time you get these symptoms get out and pump the primer and see what happens. It's never happened to me, but I've heard that that test could point to a weak lift pump, which I understand is not too terribly difficult to r&r. Good luck.

__________________

1998 E300D, 287k, barely broken in.

I vote air. Try a week of diesel fuel. If that fixes it, use electric or coolant heat to heat your fuel line. 160F is a frequently mentioned target temp for pre-injection VO. Keep in mind the fact that you're pulling a gallon or so per minute of your VO blend thru a 10 foot straw and jamming it back through another- expect a little head loss.

Feel no obligation to listen, but many predict doom for single-tankers or high percentage blenders such as yourselves. Some may cite their own experience, I can't be sure. Whether doom is clothed in sticky rings or crank-case mayonaise, I cannot say for sure.

Frybrid, greasecar or plantdrive kits may extend the useful life of your engine, depending on your belief in that demon: polymerization.

If you hit a search engine with "john galt upflow", you will find references to another greaser's bugaboo: emulsified water, and a simple solution.

Cheers!

Thanks for everyone's input and I hope for anyone else that is going through this that they find an easier fix than I.
To recap my situation, our 1985 300D runs wonderfully until after about 7-10 mins of greater than 60 mph or uphills with a heavy load on the engine. It then sputters and will not respond to pushing on the throttle. It gradually slows to a stop with the engine struggling and then when I open up the hood there is almost no fuel in the clear pre filter. I installed an auxiliary boost fuel pump back on the tank outlet which seemed to solve the problem for about 2 weeks and 2 tanks of fuel. Now, I see bubbles again coming up from my lift pump in the clear filter just before the primer pump when I rev the engine in neutral.
My wife and I have done the the following to the car: replaced all fuel lines and very thoroughly tightened all clamps, new primer pump, removed tank screen which was 99% clear, replaced all filters last week, cleaned fuel injectors (monark), and ran a tank of regular diesel through the car which had the exact same symptoms at the same time as the veggie oil we usually use. We thin our good quality oil with 20% Jet A fuel, 5 % unleaded gasoline, fuel injector cleaner and cetane boost. It's good quality stuff and I do not think it has anything to do with this problem. Also, I'm in Pensacola, FL so it has consistently been 90+ degrees outside with this problem occuring so gelling is not hardly an issue.
I think I have narrowed the problem to a bad lift pump which is forcing air into the fuel line backwards somehow. Has anyone rebuilt one of these lift pumps with the kit on this site? I know for a new lift pump its not cheap ($150-250 at least) so I really don't want to replace it unless its necessary.
Thanks again for any input.
Brandon and Megan Oswald
1979 300D
1985 300D Turbo

The kit for the lift pump is not expensive. No harm in eliminating it as a possible problem source. One of the internal pump valves could be marginal for example and become more so with temperature. Before that point in the system nothing is that temperature sensitive anyways I beleive.

I believe the kit is pretty inclusive. The small string of air bubbles observed might easily increase in size or frequency with temperature. I think there is an item in the archives about kitting the lift pump. .

My understanding that it is also not a difficult job at all to kit it. I have never done one myself though. Any evidence of reverse surging is an indication the lift pump has a problem. . You are not the first to mention this effect.

A test that might help isolate it is to pour some really cold water on the lift pump to see if it restores it to full operation when it appears dysfunctional. . The water should be kept off the injection pump top area. Possible thermal distortion issues could occur.

Another item that may identify the lift pump as the culprit as well is to spray the lift pump with liquid freeze spray when the car is acting up. That stuff available at electronic suppliers pulls temperatures way down pretty fast. I have used it a lot over the years. I also happen to believe everyone who services a lot of their own possesions should keep a small spray can of it around. No superior item for troubleshooting thermal related problems in many cases. Keep it away from kids though as they could give themselves frostbite if playing with it.

The best test although not totally conclusive is an output fuel pressure gauge on the lift pump. I say not conclusive as air can be leaking into that pump and be pressurised as well. Most likely the cause of your problem is the check valve that stops reverse flow in the lift pump. Thats if the problem indeed is in the lift pump.

Your problem is obviously temperature/time related and you have isolated it to the fuel system. Another obscure source. The crankcase breather being obstructed. Then the engines blowby allows the increased crankcase pressure to shut done the injection pump. But in that case you would still have fuel in your primary filter so it is totally discounted.