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1978 280SE
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Discussion Starter #1
Hello all. I just had a 1985 280TE shipped from California to Indiana. I am told it ran fine when loaded on the truck. When unloaded it started fine. However, when the accelerator is pushed the engine does not respond. I am not very mechanically inclined. (Possibly bought the wrong car. :) ) I had my wife push the accelerator while I looked at the linkage. Attached is a photo. When the accelerator is pushed (A) rotates however it does not engage and move (B). When (B) is manually moved the engine responds as expected and revs. I have looked for diagrams to possibly help me but so far have not figured it out. Does anyone have any suggestions where to start to diagnose more properly? Thanks in advance for your patience. Kevin
2606329
 

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1981 W123 280E "Rusty"
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Ah, German over-engineering!

How is the ball-joint linkage that runs vertically down the firewall? At the end of it, there is a rubber bushing that may somehow be disconnected. The plastic bracket that mounts the accelerator "bar" (a thick metal bar that pivots through the firewall, it has the rubber bushing on one end, the accelerator pedal slides along its lower section) may also be damaged. I assume your car's problem could be temporarily repaired with zip ties, just so you can drive it.

I had nothing better to do, so I made a lousy little diagram in Microsoft Paint. Might this be of help?
2606339
 

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1978 280SE
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15 Posts
Discussion Starter #3
Ah, German over-engineering!

How is the ball-joint linkage that runs vertically down the firewall? At the end of it, there is a rubber bushing that may somehow be disconnected. The plastic bracket that mounts the accelerator "bar" (a thick metal bar that pivots through the firewall, it has the rubber bushing on one end, the accelerator pedal slides along its lower section) may also be damaged. I assume your car's problem could be temporarily repaired with zip ties, just so you can drive it.

I had nothing better to do, so I made a lousy little diagram in Microsoft Paint. Might this be of help?
View attachment 2606339
[/QUOTE]

Thank you so much. I really appreciate the thoughts and diagram. I'll take a look at it when I get home.
 

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1978 280SE
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15 Posts
Discussion Starter #4
Ah, German over-engineering!

How is the ball-joint linkage that runs vertically down the firewall? At the end of it, there is a rubber bushing that may somehow be disconnected. The plastic bracket that mounts the accelerator "bar" (a thick metal bar that pivots through the firewall, it has the rubber bushing on one end, the accelerator pedal slides along its lower section) may also be damaged. I assume your car's problem could be temporarily repaired with zip ties, just so you can drive it.

I had nothing better to do, so I made a lousy little diagram in Microsoft Paint. Might this be of help?
View attachment 2606339
THANKS!!
 

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1981 W123 280E "Rusty"
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133 Posts
You are quite welcome!

When you find out what the problem is, PLEASE put it up on here! I am particularly curious to find out what it is, as I have never seen or heard of a physically broken throttle linkage.

If it is actually broken, I'll bet you a rust-free W116 that you can fix it with zip ties.
 

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1978 280SE
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15 Posts
Discussion Starter #6
I will for sure update the thread. Last year I paid too much for a 1978 280SE in great shape other that the fact that the heat works all of the time. It has the climate control system that apparently is is a bit temperamental and looks like an expensive fix. When I bought it the guy I bought it from said "the heat works but the air conditioner does not". Unfortunately he failed to mention that the heat works 100% of the time! Last week I bough my 1985 280TE and when it arrived in Indiana from California it won't drive at all. At least it's a wagon so I'll have a place to sleep when my wife kicks me out. :)
 

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1985 300 TD 1981 300 SD
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320 Posts
For the heat issue in your 280 I would go straight to the mono valve and which is connected to the coolant lines on the pass side fire wall and first check if the electrical connection is good. If that is fine then I would get either a replacement core or complete mono valve from Mercedes, ( usually a core is all you need), then at least you can adjust or turn off the heat if if the ac side isn't working.
As for the throttle linkage Borg has you covered there.
Something else I would check and clean while under the hood is the fuse box, dirty/corroded contacts & fuses have caused lots of gremlins to appear in these cars.
 

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1981 W123 280E "Rusty"
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I have re-analyzed your problem, and I would like to slightly adjust my answer.

Did you say that the lower linkages were working, or that the whole linkage system worked until it got to the accelerator pedal when you operated it from the engine compartment? After looking at the picture more closely, it looks like the rotating linkage rod that protrudes out from the bulkhead may be detached at where it is supposed to have a flexible coupling. I had a similar problem, and I solved it with, you guessed it, ZIP TIES! So, just take a look at that area near the top of the engine, and see if you can detect anything suspect.

My throttle linkage, if you need a reference. I apologise for the missing parts and inexplicable wiring, that's this car's nature.
2606357
 

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1978 280SE
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Discussion Starter #9
For the heat issue in your 280 I would go straight to the mono valve and which is connected to the coolant lines on the pass side fire wall and first check if the electrical connection is good. If that is fine then I would get either a replacement core or complete mono valve from Mercedes, ( usually a core is all you need), then at least you can adjust or turn off the heat if if the ac side isn't working.
As for the throttle linkage Borg has you covered there.
Something else I would check and clean while under the hood is the fuse box, dirty/corroded contacts & fuses have caused lots of gremlins to appear in these cars.
Thanks! I’ll check the fuses as well. I already see I am having some issues with lights and turn signals.
 

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1978 280SE
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Discussion Starter #10
I have re-analyzed your problem, and I would like to slightly adjust my answer.

Did you say that the lower linkages were working, or that the whole linkage system worked until it got to the accelerator pedal when you operated it from the engine compartment? After looking at the picture more closely, it looks like the rotating linkage rod that protrudes out from the bulkhead may be detached at where it is supposed to have a flexible coupling. I had a similar problem, and I solved it with, you guessed it, ZIP TIES! So, just take a look at that area near the top of the engine, and see if you can detect anything suspect.

My throttle linkage, if you need a reference. I apologise for the missing parts and inexplicable wiring, that's this car's nature.
View attachment 2606357
Yup! You guessed it. It had come loose. Once I removed the air cleaner I had a better view. Thanks for noticing it was mid-aligned. Zip ties fixed it. I think I’ll throw a few in the glove box. Thanks much!
 

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1981 W123 280E "Rusty"
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133 Posts
Did you get pictures of the linkage works before you installed the zip ties? I'm curious what it looked like up close, and exactly how it managed to disconnect itself in the first place.

Nice going with the repair!
 

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1978 280SE
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Discussion Starter #12
Did you get pictures of the linkage works before you installed the zip ties? I'm curious what it looked like up close, and exactly how it managed to disconnect itself in the first place.

Nice going with the repair!
I did not. I will need to look further when I get home next week. It doesn't seem like the zip ties will hold as close as needed and there is possibility of coming out of placement again. I will post more photos next week.
 

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1978 280SE
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Discussion Starter #13
I did not. I will need to look further when I get home next week. It doesn't seem like the zip ties will hold as close as needed and there is possibility of coming out of placement again. I will post more photos next week.
I went ahead and broke down on got the needed part. It's all in and working fine. Thanks again for pointing me in the right direction.
 

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1981 W123 280E "Rusty"
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Fascinating.

Was it just the bushing that had failed and let the rod move all over the place? That makes little sense to me, since my bushing is shot as well and all I had was a little extra play in the throttle linkage (nothing those zip ties couldn't fix!).

Now that you have the car fully functional, how does the accelerator feel on the road? One thing that drives me nuts, personally, is when a throttle pedal feels sticky when it is depressed, on any car. I figure the linkages on the M110 280s could get pretty annoying after many years, considering how many pivot points they have that could possibly wear out or seize up. Yours isn't like that, is it?
 

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1978 280SE
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Discussion Starter #15
My plastic bushing was pretty much totally disintegrated with just a small bit remaining and not serving any purpose. That caused the linkage to disengage somewhat. Seems to be fine and responsive now. Sorta hard to tell with all the other issues distracting me :) . I bought the car site unseen with no inspection from a less than forthright seller. You would think I would have learned from my other automobile purchases but I haven't. Thanks, Kevin
 

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1990 560 SEC 1985 300CD
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1,398 Posts
While you're in there messing around, it's considered good form to lube all the linkage pivot points occasionally. It's probably been neglected. Pop the connectors apart, one at a time. Clean out the crud in the cup. Snap them back together and add a few drops of ATF or light oil.
 

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1981 W123 280E "Rusty"
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Great advice. The first time I oiled my linkages, the difference it made was profound. So much so, that I had to sit in the car and just press the accelerator a few times, to get used to the change. Yes, mine was bad.

I am under the impression that the pivot points with plastic bushings fit into them shouldn't be oiled with ATF, but rather, power steering fluid. I heard once that it reacts safely with rubber parts (because there are many in the PS system), and in turn, plastic parts. I also heard that regular petroleum-based oils and lubricants can actually dissolve plastic parts. I am probably superstitious, but playing it safe has worked out well for me!
 
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