so i finally got a 300td. it is a 1984 in good condition. the turbo dosent work nor does the kickdown switch. it is slowwww. i have checked the alda line about five times, its clean. i replaced all the filters. no change. i looked at the actual turbo and it spins. i am almost stumped. i played with the alda adjustment but not much(quarter turn no difference). as far as the kickdown switch, i have heard it is tied into the ac wiring somehow? is this true? my ac fan dosent come on even tho the fuse is good. i also replaced the actaul kickdown switch to no avail.

what should i do? any help is appreciated.

When you stated "checked the alda line" did you pull the bolts at both ends and ensure boost pressure is getting to the alda? Have you cleaned the overboost protection switch?

Kickdown switch is tied into the ac wiring? I've studied the diagrams http://mb.braingears.com and have not a clue on that one.

Have you checked transmission fluid levels and adjustments?

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Sam

84 300SD 350K+ miles ( Blue Belle )

i took both ends off. how can i determine if the boost is getting there or not? do i turn the car on? i took off the overboost protection switch and replaced it with one that is functional... i think. how would i clean it? would the turbo not work if the overboost protector was not getting electricity?

adjusted the ALDA?

Forget the ALDA adjustment.

You need to obtain a boost gauge and T it into the ALDA line and then drive the vehicle.

Only then can we determine whether the ALDA is receiving the proper boost signal and what to do about it.

i suggest putting the boost fitting into the manifold itself, it is a 1/8 npt fitting, ace sells the right fittins, use brass,

1/8 npt street elbow or the same size but a hose barb.. i used 1/4 " barb ... bought the guage at autozone for 50$. right now its hanging out in my left side AC vent

Where in the IM do you put the fitting? is it a T off the same fitting as the banjo or is there another place for it?

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Mitch
1984 300D Turbo Diesel 265,000 miles
Previously Owned
1969 280SE 4.5 (what a great car!)
1979 450SL (was fun but a real gas guzzler - bought and sold on eBay)

I suggest not.

You wish to determine if the ALDA is receiving the boost signal. Connecting a simple T to the ALDA line requires no hardware and you can easily route the gauge into the cabin to observe it while driving.

If the ALDA gets no signal, then you can thoroughly clean the lines and/or bypass the overboost valve if they are suspect.

if you notice on the manifold on the long section.. their is a plug.. takes a 5mm or something smaller(Cant rember right now) hex... remove it and you have an open port to plug something into like a boost guage.. its located on the rear right by the transmission dip stick

Let me try. TheDon, connecting the boost gauge directly to the manifold at the port on the rear is fine if all you want is to read boost. What we want to do is some diagnostic work and see if that boost is getting all the way to the ALDA thereby increasing fuel availability during acceleration. If not, then the line can be cleared or the parts replaced as necessary to get boost TO the ALDA.
Capiche?

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

sorry i did not catch on mon capitaine

OK, TheDon gets it now, Great! Actually me non comprende Italiano.

Also check for end play in the turbo shaft, from front to back it shouldn't move just a few thou. If it drags on the ends then it won't spin up hardly at all.
I have seen an ALDA out of whack to where the engine wouldn't spin the turbo up. Just a tweak (actually I shimmed it) and the car came to life. You can break the ALDa capsule if you crank the shaft IN too far then its going to need a new one. Turning it out (CCW) makes for more fuel.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

about the kickdown being involved with the HVAC: On my '83 300D the transmission kickdown runs off one of the climate control fuses (#8 or #14 I think). I had a pinched/shorted wire going under the transmission and every time I floored it, it would blow the fuse and put the climate control in the fail-safe (defrost) mode. Took me awhile to figure it out. I also have had to replace the solenoid in the transmission of my 560SL. Not a bad job.

Pull the big plastic elbow off the inlet to the turbo, get a god light and actually look at the impeller (engine OFF). See if the blades are actually touching the housing. I have seen blades really worn from bad bearings. If they look ok, then you can check for axial and radial play in the shaft. One more thought, how is your wastegate? not stuck open is it?