Recurring power loss problem on 1984 300D (runs on WVO, has injection line heaters, in-line heater and auxiliary 12 v. pump before filter):
Power loss is worst/most noticable at high speeds (on freeway) and up long grades. Worst case it got down to 7mph on freeway shoulder.
Weird: If car rests for 20 minutes, gets going fine again for 10-20 miles.
Changed all filters more than once, bled system properly. Still happened.
Poured ATF into tank and directly into spin-on filter. Made marked difference for 20-30 miles, then problem recurs.
Had tank and tank screen cleaned out, thought it must be dirt coming form tank. No change.
Had injectors cleaned. No change.
Thought I found leaking fuel line, was just overflow line.
Asked mechanic to check all fuel lines for leaks drawing air. Factory trained MB mech for over 25 years, says significant air leak would cause car not to start at all. Saw threads here that seem to think otherwise (power loss thread started by tc art). What's the truth?
Any ideas? Could it be the main fuel pump (IP?) Is there a way to check the IP without replacing it? Why would ATF make it temporarily better if it's a failing pump? This is the part that stumps me.
Saw good thread here about power loss related to a misaligned throttle linkage, will check that too. (same, tc art thread)
p.s. hand pump doesn't seem to be leaking.
p.p.s. hand pump on my other MB, the wagon, IS leaking, has experienced occassional power loss, but after running some diesel through it, seems fine again, although still leaking.
p.p.p.s IF I got some bad (hydrogenated) oil in the system (small amount is possible), could clog and cause power loss or blockage in a fuel line I think, but could be "burned out" with diesel (and would have seen more problems in wagon, since both cars use same oil.)
appreciate any help from you guys
thanks so much
Stanya

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1982 300TD, 265k
1984 300D, 282k

How does it run on pump diesel?

If WVO od SVO oil has some water in it, IP could get cavitation of it's bores.

How are the fuel return lines?

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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

Can you add a clear filter or hose? I think you are getting air in the system. I use a inline fuel filter from pepboys to help detect leaks. Does it happen on grease only or diesel or both? Can you describe your system?

Mike

Hi gents, I had similiar problems on my Benz which stymied me for quite awhile recently. I started having low power alot on pull out or even at cruise. I pulled tank, cleaned it, replaced screenvery bad) and filters. Things were great for awhile, then same problem again. after much pondering I checked throttle linkage. I found that after about !/3 throttle movement the cable for boost pressure from ex. manifold would jam the link on vacuum valve against heater hose. I spot tied it to an inj. line, rechecked throttle movement thru entire range, no biding. been great ever since. After cleaning cable the last time I routed the cable inside of button on alda instead of outside towards radiator. It helps when you put problems in when fixing something, ha, ha

newagon, are you running a two tank system? If not pull the tank screen out and clean it? Make sure to put on a new o-ring, you don't want it to leak.

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thanks for replies.
rrgrassi: return lines were ok, but will check again. going to take car back from mechanic today so I can test it running on diesel. water in oil could be possible i suppose. how fast does the cavitation occur? how to fix? i'm thinking it might be something else though, because wagon didn't have same probs (although wagon has big Davco filter, maybe it does some water separating too, i'll check.)
thanks!
mike0000: i have a clear inline filter (the pre filter) and it just shows regular bubble, no extra air so far.
the conversion on this one is most basic: Vegtherm inline heater from Plantdrive, 12 v. pump before spin-on, and injection line heaters. That's it. My wagon has no inline heater, just coolant warmed Davco fuel pro filter with 10 micron big filter, then injection line heaters.
will do diesel test today and report back.
bubbazook2: thanks for throttle linkage info. had heard this before, will check today.
Biodiesel 300TD: unfortunately it's NOT the tank screen, did tank and screen clean out. even added a few extra larger holes in tank screen to allow SVO through.
ALL: will report back later after stealing car back from mechanic today to some of my own testing acc toall your thoughts.

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1982 300TD, 265k
1984 300D, 282k