Unknown reversed wires puzzle 560SEL
 

My can is 560SEL 1989. After changing injectors, spark plugs/wires and some other parts such as fuel accumulator, after that I noticed two problems:

1. The car will not start until I reverse the EHA wires in the opposite position. If the car was hot it will start but rough.
2. The trip cluster that indicates the current fuel consumption is reversed. That means when I accelerate it indicates low fuel consumption and when I release the fuel pedal it indicates high fuel consumption.

I tried my best on that car but it was useless. I don't remember that I reversed any wires. Have anyone faced such problem before?

This is a real mystery at leat for me.

I know it's not a common problem and hard to get fixed or even to start to fix :)

If that is in fact the problem, simply pop open the plastic connector housing and reverse the pins and snap it closed. Done.

What is a "trip cluster that indicates fuel consumption"? - I have no idea what you are talking about.

Isn't the economy gauge vaccuum actuated? maybe some kind of vaccuum line is somehow disconnected or reversed. ( if that's even possible)

It sounds like you knocked the cabin vacuum line loose - back of the intake manifold, and the vacuum aka economy gauge is reading zero. This will cause a vacuum leak.

did you check the vaccum lines right around the firewall closest to the engine?

The economy gauge is controlled electronically not via vacuum. The trip cluster is very rare in W126. I attached its picture.

Oh. One of those doomahickeys. nevermind

Ditto, never seen one. But it still may need vacuum to operate.

Where do they mount that thing in the car? Never seen one. Is it an option from MB?

it operates without vacuum. There is a computer to control it. Yes it's a very rare option on W126 and is mounted on the instrument cluster exactly in the RPM place where the RPM is moved to the left side. I'll try to snap a photo soon for you :)