MB w113 230SL to 560SL body wiring harness conversion

[lpeterssen]

Dear friends

Hereafter I will try to reflect the best I can my recent experience in building a full wiring harness set for a customer who bought a w113-230SL with a R107-560SL drivetrain transplant.

The car was bought at an auction since previous owner left the project un-concluded.

This particular job which as you know, I do like a hobby/side business, was a huge challenge for me since I have never before accomplished a wiring harness modification about this scale. It took me 12 continuous days to actually finish the job not counting the days I dedicated to study all the diagrams before the wiring harness arrived to Venezuela (it came through a cargo forwarder by airfreight, only 105$ for 20 lb and was here fast in 7 days).

As you may already noticed I like things that make me think and plan ahead. This is exactly the case, so I am grateful of having finished a project this complex.

Well…… let’s go without further do right to the point.

230SL is quite different from a 560SL 88’ which runs on the KE-jetronic engine management system with a close  loop emission control hardware.

The customer sent me the main body harness for the 230SL-Auto plus an used 560SL engine wiring harness.   For the transmission control he sent me only the photos of the wiring harness cable ends with the terminals opened so that I could contrast pictures against wiring diagrams.

Of course for a project like this,  the first thing to do is to source the wiring diagrams for the car drivetrain you are trying to implement on your loved MB Pagoda.  The w113 diagrams are already available on this forum, so that part is easy.  For that purpose, searching on internet, I found that www.mbmanuals.com have a great selection of wiring diagrams at a very reasonable cost.  Also, there are some others resources like the r107 fan forums, etc where some other diagrams can be downloaded many times for free.

There is no single  wiring diagram that will show all the information you need to decide on which direction are you going to go for customizing the w113-230SL main body harness to successfully communicate with the R107-560SL engine management harness.  The information needed is therefore, atomized or disperse among many many wiring diagrams.

The Mercedes so called ETM electrical troubleshooting manual is among my favorites, and I strongly recommend to have them always for this kind of projects.

Once you have all the possible wiring diagrams you have to study them many times passing through each of the systems that make a car work,……..again and again and again

An internal combustion engine needs as all you know, power, fuel supply, a startup system ( start logic) and ignition.  Study all those systems, that on a modern car like 560SL, do not appear on a single schematics.


FIRST
====
The first thing to do is to see what w113-230SL legacy systems will no longer needed, and clear them out from your barebones body wiring harness. On this particular case the obvious things to be eliminated were:

1. External alternator voltage regulation lines
2. intake IDDLE switch
3. intake IDDLE increase selenoid terminals
4. Intake CSV cold start valve
5. Fuel enrichment selenoid terminals
6. Cold start relays terminals
7. TTS terminal branch
8. All wiring related to the automatic transmission, since a full new loom was built for that purpose.

SECOND
=====

After studying all the wiring diagrams related to power distribution, you will conclude that your original T30 lines are insufficient in section to feed all the new consumers included on the new drivetrain.
For that purpose, on this project we changed the original T30 lines from 4mm2 to 10mm2.  One loom went from the alternator directly to the main light switch, and another from the alternator to a junction box which afterwards passed the energy to the t30 terminal at the starter. So, we ended having two 10mm2 lines coming out of the alternator.

We noticed that original w113 ignition tumbler switch, with screwed terminals, was too restrictive for including new T30 and T15 lines, so we decided to change that tumbler switch with the newer model used on later pagodas with 8 pin round connector which has 2x ports for T30 and 2xT15.

Customer wanted to have a HVAC unit, so we needed to increase power handling by the main fuse box.

So the ignition tumbler switch which is responsible of feeding energy to all T15 circuits at the main fuse box which are not related to illumination was upgraded to have 1x2.5 mm2 line on one t30 port and another 1x2.5mm2+4mm2 t30 on the other port (will explain why this 4mm2 later).  On the switched T15 side we have installed 2x 2.5mm2 lines which went from the tumbler switch to the main fuse box.  So total t15 was 5mm2.

We used the ignition tumbler switch as a T30 hub to feed energy demands from the 560SL engine management harness. So that extra 4mm2 cable was for that purpose.

THIRD
====

Fuel delivery.  On a W113 fuel pump is directly fed by fuse no.4.  A 560SL has a totally different approach where fuel pump is fully controlled by an ECU called fuel pump relay which has about 12 pin terminals as it collects data from many sources to decide if power is sent to fuel pump or not.   So the fuel pump circuit on the 230SL has to be fully rebuilt bringing T30 power directly to the fuel pump relay and collecting the relay output and routing a new wire from there to the interconnection 12 pin connector to the  body rear wiring harness.

FOURTH
=====

Bringing power to the engine control harness.  There is a so called OVERVOLTAGE PROTECTION relay which is responsible of bringing power to all 560SL ECU’s. That relay together with the fuel pump relay was fed from the ignition tumbler switch with a 4 mm2 T30 line.

Fifth’s
=====

Communications between the two harnesses.  After much study there are basically two ports on which signals pass from body harness to the engine control harness and transmission harness.  Those are the X26 terminal and X49/2 terminal for the transmission.

You have to study a lot the diagrams to pin point what signal goes on each pin. Again the information is scattered among many diagrams.

There are 14 pins on terminal X26 And 8 pins on the transmission X49/2 terminal.

That pin assignment is reserved to my personal knowledge.


Well my MB colleagues, all described among these lines will give you a general idea of the titanic work involved in a project like this.

Your thinking in order to solve this puzzle should always go from GENERAL TO SPECIFIC.  You have to analysis one system at at time a completely solve it,  before taking over the next system.

Here a link of the report prepared to the customer:
https://www.dropbox.com/s/y414od5o13ufck6/230SL%20to%20560SL%20conversion%20report.pdf?dl=0

And here, finally a link to the shared photo album where the actual work can be appreciated

https://www.icloud.com/sharedalbum/#B0Q5epZ6aK6SRO


Best regards
Eng. Leonardo Peterssen

[BobH]

Blimey Leo, i think this customer was very, very lucky to have found you, i can't imagine many auto electrical engineers would have taken this on!

[lpeterssen]

Dear Bob

Thanks for your comment.  Yes I think the customer was very happy to find someone willing to take the case of study.

Best regards
L.Peterssen

[stickandrudderman]

It is indeed a significant achievement. The reason that professionals won't take work like this is because it requires single minded focus and time; lots of time.
You might find a customer willing to pay for your time but you've also got to have all of your other customers be prepared to not be served and yet remain loyal whilst you devote your time to such a project.
If I was retired and bored I'd love to do work that required the creative thinking that Leo is amply demonstrating.

[lpeterssen]

Dear Colin

Thank you for that huge comment. Very positive and coming from a well known MB authority as you, makes it much more significant.

Best regards
L.Peterssen

[Jack the Knife]

This is incredible. The world is blessed to have guys like you who are willing to do the deepest of dives into very challenging subjects.

Do you have any photos of this 5.6L-swapped 230SL? Is it just the drivetrain and such or did he also swap in the rear end? The latter is possible, but requires cutting of the subframe. Nonetheless, the 560SL's rear is a significant improvement over what came in the pagoda, obviously.

[Peter van Es]

Hi Leonard,

great research and diagnosis work. As Stick writes, customers are not always prepared to pay for the hours invested in gaining the knowledge and therefore these projects fail or stall.

I think cars with ECU’s and other control computers, from the 80’s onwards, will be very hard to restore if the electronics fail. As an electronics engineer turned software guy, I sometimes think of an AI network, monitoring all signals coming in and out of a controlling device, learning to correlate inputs and outputs, and then subsequently implementing that in one of todays powerful microcontrollers, available at around the US$ 20-30 mark so that a defective device can be replaced.

However, implementing something like that generically will cost tremendous amounts of time, yet could make a whole population of cars restorable.

Thanks for sharing your insights

Peter

[lpeterssen]

Hi Peter

Many thanks for your comments, I really appreciate them.

Of course I didn’t bill the customers all the hours invested on the research..   I did the job as deep thinking exercise.

Interesting your idea of AI monitoring signals on different devices to learn about its functionality and correlation.

 Best regards
L.Peterssen

[lpeterssen]

This is incredible. The world is blessed to have guys like you who are willing to do the deepest of dives into very challenging subjects.

Do you have any photos of this 5.6L-swapped 230SL? Is it just the drivetrain and such or did he also swap in the rear end? The latter is possible, but requires cutting of the subframe. Nonetheless, the 560SL's rear is a significant improvement over what came in the pagoda, obviously.

Dear Jack

I have photos of the engine bay and car in general but have to ask permission to customer to publish them.

I think the car just received the engine and transmission of an automatic 560SL.   I doubt the car rear end was changed towards the R107. I think that part is still w113 alike.

Best Regards
L.Peterssen