My wife has been driving our 85 the 35 mile trip to work everyday and has had the same problem twice now in the last couple days. After about 25 mins of driving at 70 mph, the car would lose power like a clogged fuel filter. I drove it today and it started to do the same thing after about 30 mins of driving when I floored it up a steep hill near our house at about 55mph. The fuel filters are both fresh with a new priming pump and the air filter is clean.
I have not bench tested these injectors yet but the car has wonderful, smooth power until the above problem occurs and consistently gets greater than 25mpg. It runs at 80-90* C consistently as well. We are running it on veggie oil. I also have not checked the fuel tank strainer.
Please help! I already ordered Monark nozzles for it and will install those and clean the fuel tank strainer next weekend.
Any ideas??!!
Brandon
Pensacola, FL
1979 300D "Red"
1985 300D Turbo "Blue"

Hmmmm...maybe the cap isn't venting, and you are getting a vacuum in the fuel tank?

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

I tried running it today with the fuel tank cap off and had the same results. I should mention that this only occurs at high speeds above 50mph or flooring it going up hills or just trying to accelerate out of an uphill stoplight. If I slow down or reset to about half throttle, the problem subsides.
What gives?
Thanks,
Brandon

Can you switch back to petro- or biodiesel to see if it has anything to do with the veggie oil or its system?

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Yes, try regular diesel. You could be a victim of air in the fuel system also.

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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 TD Turbo, chipped. Still needs EGR Delete, 228K

90 Dodge D250 5.9 Cummins/5 speed. 400K

It could be a lack of fuel or air (boost).
run a long hose from a tee on the back of the intake manifold (on the so called ALDA line) into the cabin and watch a pressure gauge there while you drive. Read the boost cold and then as the car heats up. If boost is dimishing as the car gets hot, then you may have a faulty wastegate. When the spring in the wastegate valve assy heats up it can lose tension and reduce boost (by dumping it). Easy to diagnose and easy to miss if you aren't experienced with the boost system.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

After replacing both fuel filters again, pulling the fuel strainer (which was 98% clear), checking vacuum readings, replacing the stock airbox with a high quality aftermarket kit, cleaning banjo fitting for ALDA, adjusting ALDA in small increments, and trying different transmission throttle position cable settings, our 1985 300D is STILL doing the same sputtering and eventual dying after it gets to about 70-80*C.
I also drove it with a guage attached to the boost line that goes to the ALDA. I got 9.5 lbs of boost at full throttle and consistent readings until the engine warmed up but when it started to sputter, the boost pressure dropped correspondingly. I'm not sure, but it looked like it was dropping as the engine spooled down which would indicate to me that the turbo and the wastegate are working fine and are not the culprit.
My wife and I normally run both our 300D's on veggie oil that we thin with 10% Jet A and 5% unleaded fuel, cetane boost, and injector cleaner. We filter it down to 5 microns and run it through a water block before putting it in the tank. I do not believe this is the problem because I filled it up with regular pump diesel on Friday and it is still consistently doing the same thing.
CAN ANYONE HELP?? I'm tearing my &*$^@#* hair out because of how well it runs until it heats up. I don't get it!!!
Should I maybe splice in a fuel pressure guage and monitor that?? Wouldn't air getting in my fuel lines affect perfmormance regardless of temperature?
I feel like I'm missing something obvious but everytime I stand there looking at the engine everything looks and checks fine.
Thanks very much for anything you can contribute,
Brandon and Megan Oswald
Pensacola, FL
1985 300D Turbo
1979 300D

I forgot to mention also that when we came to a stop today after test driving, the car was in neutal but the driveshaft was making a banging noise. I got under the car and sure enough the driveshaft looked like it was trying to engage the rear end but was just hitting it. I had my wife put in park and it continued to do it there as well. It also got slightly louder as she stepped on the gas.
Think this has anything to do with the sputtering and dying problem?? I does shift somewhat firmly but doesn't seem too bad. Also, when it starts to sputter it won't shift up or down at all.

Thanks again,
Brandon Oswald

As a diagnostic procedure, I would hook up an alternative fuel supply in a bottle under the hood, disconnecting the regular tank and all its fuel lines. I'd then drive it on the alternative fuel supply. If it runs ok then you know the problem is in regular fuel supply. If the condition persists, it would seem to indicate a problem at the engine itself.

I don't understand what you were describing with the driveshaft but it doesn't sound good.

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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

Thanks for the reply. I will try that today. Makes sense to isolate half the fuel system at least.
The driveshaft was trying to spin when the transmission was in neutral and when it was in park. What could make it do that? The fluid is worn but I don't think that alone would cause this. Could it be a vacuum or throttle position cable sensor issue?
Thanks again,
Brandon Oswald

I think you are sucking air thru some part of your system, the leak is probably exacerbated by the heat of an operating temperature engine.... does the primary fuel filter ever get a big air bubble?

Creep in neutral is normal, and perhaps parking pawls were not fully engaged, either way, forget about it till you rule out the fuel system.

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Cheers,
Robert

Ok, we're still having issues with the 85 300D. Here's what happened today: My husband drove to work, mostly stop and go traffic, and about a 45-50 min trip. He had a constant speed of about 60mph for 4-5 minutes after the car was at NOT (normal operating temp) and then it started to sputter. He pushed the pedal down and you could hear the engine downshift and rev up but the car was still decelerating. Once the car shifted to a higher gear there was a greater loss of power and the sputtering got worse. He had to go down a large hill so he kept a constant throttle position and when he headed back up the hill at 1/2 throttle the sputtering got worse. He then had another mile or so to go at 25mph and the car barely made it. Once the sputtering gets too bad, even if we shift into neutral the car typically dies. After about 3-5 min with the engine off and the hood up, the car will crank easily and accelerate swiftly but will begin to sputter again soon. I know we've posted a lot about this and I'm afraid we're just not describing the problem well enough for all of you to understand. Several people have mentioned the injector pump but not specifically what we should do. Please help with specific troubleshooting if possible...we're both pulling our hair out over this!!!!

Thanks, Megan and Brandon

Did you try the alternate fuel supply?

__________________
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

yes, and that worked, but we also may not have driven it long enough to cause the condition to reoccur. I think we'll try it again and really put a load on it.

I forgot to mention...each time we try something it appears to fix the problem temporarily...or we're just not test driving it long enough for the symptoms to arise. We'll try the alt fuel supply and take it out on the highway.