It's been quite some time since I drove my 91 up any serious hills. But did so just recently and was surprised by the difficulty it had and my need to shift into second gear from time to time.

On the relatively level ground on which I normally travel, I don't notice any issues at all...power and acceleration seem fine.

Just curious what any of the rest of you experience in your W124.

It's been 21k since I changed the main fuel filter, so I'll so that. Might tinker with the ALDA at some point.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Mine did, but then I found out I had a vacuum leak that caused my waste gate to stay open. The story goes that the car felt under powered, even through I replaced my injector nozzles with Monark nozzle which should have provided more power, but still the car would have trouble going pull/maintain speed going up hill. I installed a temporary boost gauge to check my boost level and I found out that I barely made 10 psi at full throttle. So I did the pressure actuate waste gate mod and when doing so I found a split in the vacuum line to the waste gate. Anyway, I completed the mod, now I almost make one bar and the car drives awesome. I also did a 2.5 inch straight pipe exhaust with a Brabus style tips, the car sounds awesome too.

I've done the wastegate mod...so I can rule that out. But I know turbo can get carbon build up and thus have trouble spooling up.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

clean the tank filter.

If auto what mode is the shift set on E or S . Put it on to S and try the hill again see if is any better .

It's a 722.4....so my choices are D, 3, and 2.

I'm hoping it's just the fuel filter....will change today. The only reason I wasn't suspecting the fuel filter is that, in my experience, a fuel filter being clogged becomes symptomatic suddenly...it's a very obvious loss of power. But perhaps it can happen more incrementally.

Another possibility is that I've become so accustomed to driving my CDI that I'm judging my W124 unfairly. My impressions are obviously very subjective.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

You could do a 0 - 60 run and compare to published times. ( Deducting for engine wear. )

Fuel filters clog gradually but until engine fuel requirements exceed fuel flow, the restriction will go unnoticed until power drops off. If the driver never or rarely uses max power then calls for max power, the clog will appear to be sudden.

Given a diesel is throttled by fuel flow, reduced fuel will be the same as not pushing the throttle to max. On an electronic diesel, it may compensate unit it runs out of range / throw a code for low pressure.

In the late 80's when FI was becoming more common, I had customers whom bought a FI car and suddenly their old carbureted car was an undrivable mess. In reality, nothing had changed with the properly running carbureted car.

Managing customer expectations / perceptions is far more difficult than fixing any car as each customer has a different set of sometimes fluid expectations.

I changed the main filter and there seems to be an improvement. But I'm not near mountains any longer so not able to put it through its paces the way I'd like.

Thanks for the fuel filter insights, everyone.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Pic 8 looks like a way to deaerate fuel, keep the supply from picking up air when going around a corner with low fuel and , . . . a place for sludge to hide.

The tank would appear clean when looking in the sender hole but the lower tank could still be dirty.

The drawing in post #8 illustrates the setup in the TD wagon's tank system. sedan tank strainers have their output directly through its center bottom using a threaded hose bib. The sedan tank's return flows into a cup that surrounds the in-tank strainer to ensure maximum fuel at its minimal level.