At first I was going to say 'why' but I decided to do a search and now I see where you're coming from. (Seems like a pretty credible theory)

Lay beck 40 brought up a good point in this thread which I will check when I get the chance to do another bottle run.

1979 300td -- Can anybody walk me through a lift pump test?

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1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."

Every 617 I have had, it has given appreciable results.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Ok here is the current situation and diagnosis.

The good news? All signs indicate that my tank strainer is at least ok and not the source of the low power issues.

First, this is the fuel that I dumped out of the main fuel filter that I replaced just the other week. (Looks pretty bad but I didn't want to jump to conclusions so I kept going)


This is the fuel that I used for the closed circuit test


And this is what the return line brought back at the end of the test.


Here is where things get interesting though. Running off the bottle with a BRAND NEW main fuel filter had NO impact on performance whatsoever.


However before I fiddled around with the filters and bottle I decided to check the banjo bolt on the engine side of the injection pump as winmutt suggested. My spring was just around 20mm. I did a quick stretch (By hand...unscientific but this was just a test.) drove the truck and noticed better reactions to my inputs. Ok, now we're getting somewhere 8-)

I've been doing quite a bit of searching but I can't find out if anyone ever managed to find a suitable replacement spring for the banjo bolt..... (I should mention that my uncle works for a spring manufacturer and might be able to come up with something)

Here are a pair of videos of the return fuel supply which I took at the end of the bottle test.
http://www.youtube.com/watch?v=hRPDA5LwI1Q
http://www.youtube.com/watch?v=sWL5peJ4f4Q

__________________
1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."

Have you had someone sit in the wagon....while off....floor the accelerator and confirm the linkage is hitting the full throttle stop? Also not sure on a g wagon, but on the cars.....there is a firewall pivot bushing that rots and causes issues, there was also one year that Mercedes used a rubber bushing near the stop lever....which rotted....and on the euro models, where the fork goes into the stop lever....there are two plastic bushings that are usually mia and people don't know there is suppose to be a bushing there....

__________________

Already tested that. It's good.

__________________
1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."

Iirc spring should be 27mm. You can order repolacments from Bosch shops.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Does it have a part number?

(When you say Bosch shops I presume you mean general retailers? NAPA, Autozone etc?)

Bump-Does anyone know of a source for these 27mm springs?

(I can't seem to find a Bosch shop in my area)

__________________
1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."

I made and sold some adjustable fuel pressure regulators as well as fuel pressure test kits a few years ago. Not sure if I have any left. I'll look if you like.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thanks for the offer (I just read your thread on them, nice work on the adjustable models!)

Right now however my goal is to stay as stock as possible in order to narrow down the power loss. My spring is 20mm and probably just one step in the process, once I get a new spring in and see the difference i'll be able to know where to focus next.

Just stretch the spring and measure pressure before installing.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Sad to say but I don't have a pressure gauge and i'm pretty sure that the spring would just re-compress very quickly anyways.

If you get a new spring you still have to measure it to know where the pressure is set.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Have you verified as suggested earlier that both G wagens have the same differential? Best way is crawl under and read the part number.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yes they both have the same differentials.