Re: Mercedes 190e M102 UAEFI conversion

2025-10-05T22:46:31

Ok, let's keep on rolling.
Now, everything assembled on the car:

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It was time to manufacture the harness and the coil support:

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.
The fun part sadly ends here, once i got it to start and idle well (it required a full day since i misconnected 2 spark plug wires) i was starting to taste the feel of getting the conversion done! but that's were some misterious issues started appearing.

First issue, my board is plagued by the 5v loop issue that is affecting other boards, but soldering the 10k resistance to wake up the regulator worked in solving this issue.

Second issue, while i was still troubleshooting the spark plug wires issue, i got an injector (B6 output) stuck open (output from ecu always grounded), from which i got an error in tunerstudio (which showed only once, never reappeared).

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and i found resistance R29 had gone from 4.7Kohm down to 0.7 Kohm for no reason that i can see (i work with some powertrain guys from the powertrain division of a formula student team, we usually use motec but the way the ecu was handled and tested was nothing out of the ordinary).
You can see here the measured voltage across the 12v and B6 pin (which wasnt active at the time of measuring).

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I since then switched the injector 1 output from B6 to B2 to continue to use the board, and did a 45 minutes tuning session with it, everything seemed to work fine untill, after a pause, i restarted the engine and in 10 seconds in i lost both cyl 1 (output B2) and cyl 4 (output B3) injectors output.
Now the ecu shows 5.5v across these pins, no errors and testing the outputs through software doesnt change the voltage measured.
the injectors all measure 16.something ohms.
I still have to investigate the issue, but i think i'll find other resistance shorted (maybe they were defective? idk).

anyway, attached the schematics and pinout, also for other users to maybe take inspiration if needed.

EFI_wiring.pdf

If you have any kind of suggestion on what to check / change on it to make the board reliiable i'm all ears; i would happily buy another one (hoping for more reliability) but being in italy makes it kinda hard...
Anyway will have to figure it out since i need to get the car back on the road.
Thank you for your attention

Statistics: Posted by Giobs — Sun Oct 05, 2025 10:46 pm

Mercedes 190e M102 UAEFI conversion

2025-10-05T21:39:38

Hi everybody!
I'm Gioele, an Italian almost mechanical engineer (just finishing my studies, i'm still at uni) with a strong passion for both old cars and newer technologies.
I've owned this Merc for 4 years now, bought with the payouts of my first side job and it has always been a pleasure to drive around.
2 years ago i started growing an interest in powertrain related affairs (i'm a chassis guy usually), and have been wanting to convert my car since then, initially to MS but then decided to go with rusefi since it was a far more affordable option.
So yeah, 2 years in planning, untill now, when i had 2 weeks off and the conversion finally begun.

Screenshot 2025-10-05 232513.png

this is the part list.

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here's the UAefi wired into it's custom case, you can find wiring info in the attached PDF file.

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Here's the lambda, CPS and toothed wheel mounted on the car; the bung for the o2 sensor has been tig welded in the nearest position to the cylinders as possible; the toothed wheel has been mounted on the stock vibration dampener after having it lowered by 5mm, so it's squeezed between damper and pulley. The CPS is placed at 0.8mm from the wheel which has ben turned on a lathe after being laser cut to achieve as little runout as possible.

Then it was the turn of the intake manifold, got it disassembled and cleaned, then modified to house the rail/injectors, MAP/IAT sensor as well as the TPS (which is giving me some issues right now, but lets go on).
here are some picture. the mounting for the throttle link and spacers have been manufactured using the infamous "eyemeter", a grinder and a lathe.

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(i think i reached the max number of pictures on one message, keep scrolling)

Statistics: Posted by Giobs — Sun Oct 05, 2025 9:39 pm

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Re: Mercedes 190e M102 UAEFI conversion

Mercedes 190e M102 UAEFI conversion