Hi there, i`m having a weird problem with mine 87 SDL (126.125), the engine is running normal until i push the ac knob, at this very moment the engine (603.961) change sound ( kind of a bronco brull), goes up in rpm like from 650 to 800, and beging to smoke a lot (car normally does not smoke at all), the smoke is totally black and the car use a lot more diesel fuel than normal, from normally 25 mpg goes to 15 mpg with the ac on.
I do supose myself than a sensor is trigger when the engine detect the extra charge do the start of the ac and the fuel pump send a extra amount of fuel to the engine and the engine receive more fuel than needed.
Somebody also told me about a wrong conected vacuum being the cause of the problem, but i can`t tell.
Why this is happenning?, what can i do to prevent this hapenning?
Any ideas will be appreciated, i`m getting crazy after five months with this problem and after three auto mechanics charging me for a problem they can`t resolve, the smoke is so bad that the bumper and back of the car get totally black after a 50 milles drive, and here in SW Florida the diesel still is $4.30 a gallon, can you imagine what this problem is costing me, thanks for your answer.
PD: i just read a article about changing or modifiying something in the turbo wastegate who give a promptly response to the engine and more power do to increase turbo pression, what is true about it?

Well.... something is definitely screwed up there. But the injection pump is totally mechanical (excluding the idle speed control), so it is not possible for an electrical signal to be dumping excess fuel in at the touch of a button. I'm not even sure if the electronic idle speed actuator (ELR) could cause any smoke, it shouldn't have that much capacity.

I suspect something fishy with the emissions system... possibly the EGR valve getting opened when it should not? That might (?) cause smoking, as exhaust is dumped into the intake at the wrong time. It's odd that this starts when you turn on the AC. The good news is that the car runs ok otherwise, 25mpg is more or less normal for an SDL (a bit low but not bad). However, 15mpg is just awful. I would study the vacuum diagrams for your car and trace every single vacuum line under the hood. Then disconnect the EGR and ARV (air recirc valve) and plug those lines. Click here to see the vacuum diagrams, your car is covered on pages 6 and 7.

No modifications are neede to your turbo wastegate, your 1987 model has the pressure-operated wastegate, which is a good thing. You may want to look into adjusting the ALDA to increase fuel delivery off-idle (which increases power on takeoff), but I would not do this until after you fix the "smoking AC" problem!

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Dave
Boise, ID
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I`ll try tomorrow morning with the vacuums, thanks for the vacuum diagram and your expertise, i was thinking that much more electronics were involved at the IP because the three cables terminal at the end of the pump, what really make me think is the amount of extra fuel injected at the engine when i turn the AC on, what can make the IP deliver more fuel than normal ? isn`t there any other regulator like the atmosferic regulator of something similar? I have to keep trying, like any other DIY is a matter of keep trying diferents things, more tomorrow.

Hey gsxr --- thanks for posting the link. Is his car a California version? I ask because on pages 8 and 9 is the information for the 603 Federal version starting in 1986 (my car).

Thanks, again.

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daw_two
Germantown, TN

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04/2010 1965 190D(c) "Ben"
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I do have the Federal version, my car is Florida Original.

I'm nearly certain that all 1987 models have the CA emissions with both EGR and ARV. That is the only difference, the 1986 Federal versions do not have ARV, and therefore only have one vacuum transducer (Y31/1) to the EGR (60), where the CA setup has two vacuum transducers (Y31 and Y31/1) with the extra one going to the ARV on the turbo (137b). Note that there is no mention of a 1987 Federal-only version. The 1987 models all had CA emissions, for all 50 states.

I'm going to take a completely different tack with this Dave:

The engine is using significantly more fuel when the a/c is engaged. It will produce black smoke in an attempt to turn the compressor.

Ergo........the compressor is on the way out and is using much more HP than is should be using.

Explains the smoke..........and the fuel consumption. A normal SDL typically loses 1.5 mpg with the a/c in use.

Brian, it would explain the fuel consumption, but not the smoke. At idle, I still can't see how any kind of load would cause the engine to smoke that much. Not to say it isn't possible, just that it would seem strange to me. Also, if the compressor was taking THAT much power, I don't see how the belt wouldn't slip and KLIMA wouldn't deactivate it based on the RPM signal.

Anyway, the compressor should be fairly easy to test... it should turn by hand without much effort. Next up is to unplug the electrical conncetor on top of the AC compressor, and try the dash switch again. If it runs perfectly without the compressor engaged, despite the button being pushed, the compressor is definitely the top suspect.

You are alright, my car do have two vacuum transducers. And i strongly doubt that the cause of the problem is the a/c compressor, i did change it last month for a used one who has running without any problem in a w124 and it was running smoothly in my hand.
i just found out today that the vacuum amplifier (number 123 in the diagram) is leaking a very dense oil from underneath, there is not supose to be any oil in there right?, just vacuum, but anyway i doubt this can cause all that problem, the car is been running like this for quite some time w/o smoke.
Everything begon after the engine overhauling, i begin to thing they did some faulty conections somewhere in the engine when they mounted back.
For your info, the vacuum pipe "A" in the diagram (thick black pipe from vacuum transducer to cab) is cut just before the filter 62A but it seems to be so for quite sometime, in his place or better say goint into the filter 62a is one vacuum pipe coming from 67 (vacuum pump), and 61 b coming from vacuum pump (ws/bl) is cut and do have a bolt in it just before going into the vacuum transducer Y31, those are the only things out of place and this side, further, line A coming from cab (sw) is cut before going into 65 (vacuum control valve) and do have a bolt in it too but i`m sure this was so before the problem begon. Everything further seems to be in place, at least to me, good with computers but very inexperienced with car repairs.