I have been looking for a while at several W123 diesels, and test driven quite a few. Today I looked at a car that seems in quite good condition in most respects, checked all the "normal" issue spots. Drive-train seems in general good condition with very little engine blow-by. No smoke on start-up and smooth idle. Great body and interior. The one thing that stands out seems to be a lack of power coming off idle (this is in comparison to the other OM617 turbos that I have driven). There seems to be almost no torque until about 1500 rpm, at which time the engine responds normally. It does not matter if accelerator is all the way down, no black smoke or power.... At these rpm's, the turbo should not have any effect, so I think I can rule that out. Any thoughts on what could be going on? Seems that there is insufficient fuel delivery for some reason. Thanks for any comments

Search ALDA adjustment

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1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
262,715 and counting

Cleaning the pressure line, fitting and bolt from the intake manifold to the ALDA would be a good place to start.

My Car had a similar issue when I first bought it. It turned out to be way too much slack in the Throttle Linkage.
Ounce I took out as much slope as I could it ran fine.
One of the causes can be the Plastic Bushing behind the Bell Crank on the Fire wall could have gone bad.
(Engine Cold and not on) Grab hold of the Throttle Arm and hold it have someone step slowly on the Accelerator Pedal and see how much play there is in the linkage before it starts trying to move the Throttle Lever.
Release the Lever and have some on push the Accelerator Pedal all the way down and see if the Throttle Lever actually moves all the way to the Stop Screw.

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84 300D, 82 Volvo 244Gl Diesel

+1

Check the linkage first. It is often overlooked and usually out of adjustment or a component has come loose or broken.

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AJ

1985 300D (SOLD)

Thanks for your replies. The accelerator linkage seems like a likely candidate. As for plugged-up banjo bolt and line to the ALDA, maybe I don't understand the operation quite right, but in the case I describe, the intake manifold pressure is at atmospheric (or really slightly negative, considering restrictions in air filter etc), so even if there is a restriction in the line from the manifold to the ALDA, there should be no compensation for additional fuel based on boost. Cleaning out the banjo fitting, line and switchover valve is a good idea regardless. Thanks again

The additional fuel is being restricted by the ALDA. It operates with aneroid capsules that will be squeezed smaller by the turbo boost. At idle, there is little boost, but the turbo is always spinning. So if the ALDA line is partially clogged, it won't get the proper signal.

Some ALDA's have been adjusted to allow more fuel, noticeable at low rpm.

I would think a linkage issue would not allow a full pedal range.

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83 SD

84 CD

A loose or out of adjustment throttle linkage makes the car VERY sluggish. I know from experience. So do others that have had the problem. I have helped adjust the "loose" (low power) linkage problem in 4 different cars now.

It literally takes 10 seconds to check with a helper sitting in the seat and pressing the pedal to the floor. This is why I recommend doing this first before even lifting a wrench.

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AJ

1985 300D (SOLD)

gunnar 13,
Welcome to the forum. We hope that you will find it helpful. When you finally snare a 300D, be sure to post some pics & details. If you are looking at a particular one that is local to a member, be prepared to as if they know of the car. There are many very experienced people on the forum who are happy to help.

Good Luck with your hunting!!!!

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Adjusting the alda is the last thing you should do.

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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

I know on the 85 300SDs they changed the rear end from 3.0somethingish to 1 to a 2.8somethingish to 1. I don't know if they did this on the w123s. Also the 85 federal cars added a turbo with an ARV (Air Recirculation Valve) on the compressor housing for emissions. Plugging the vacuum line going to the ARV will bring back the low end.

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green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons )
white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank)
desert storm primer 63 T-bird "The Undead" (long term hibernation)

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When I bought my wagon it was a turtle off the line. I found the that the hard plastic line from the back off the intake to the to be broken. I put it back on the banjo bolt and it was a whole new car. So check both vac lines and banjo fittings from ALDA, make sure neither is broken or clogged.

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+++1
-regarding the proper throttle linkage adjustment/testing of measurements. The throttle linkage not only controls throttle (IP) response (input) but is directly related to how well and (partly) when your transmission shifts (as vacuum control valve lever moves via linkage). This also brings up the issue of having proper transmission case pressure (as it relates to proper amount of vacuum being 'teased' away from it by VCV) because an out-of-adjustment vacuum system will greatly reduce performance. It degrades over time and is seldom checked, if ever. As I understand it thanks to this great site.

I neglected to say that the ALDA should be left alone if you want your car to drive as it was designed to for many years. Some time ago I messed with mine but discovered that changing the setting merely covered up other maintenance issues I had to address. I ended up installing a virgin, used ALDA and I stay on top of diesel related tune-up issues and must say these cars run awesome with proper maintenance and care. I love my '83 300D (almost 300k)!