OM603, 722.6, and W124 adventures!
 

Hey Everyone! Just thought i'd post a quick update on some of the projects i have been working on for those interested! So all this started out with a sad 1987 300TD that was given to me in exchange for some work. It needed a lot too but i had really been wanting an OM603 powered car for awhile after running out of fun upgrades on my OM617 powered 300CD. I'll just make a list of the "upgrades" and what not i did to the TD up until now...

-replaced cracked #14 head with a fresh #22
-used a 3.5L OM603.970 injection pump full load adjusted and advanced timing
-garrett TB03 .55 trim adjusted to about 17psi peak boost
-OX- CAT replaced with straight pipe
-EGR, air flow meter and all wiring removed and tidied up
-150A bosch alternator from SL500 i had rebuilt locally with clutched pulley
-smaller OM603.970 water pump pulley, 606 turbo fan blade and clutch
-larger 10PA17C a/c compressor used with 603.970 bracket and custom hose set made. running R12 with new aluminum evap and dual fan condenser.
-1995 w124 front end look (headlights and hood)
-Ole's standalone transmission controller and 722.6
-LCA bushings and lower ball joints, everything else was ok.
-8 hole w124 wheels
-nice stereo

There is plenty more i did to it but just lots of little stuff not worth listing. The car was an utter pleasure to drive after getting the 722.6 installed and tweaked just right. I drive a ton, mostly highway and this thing just loves it. With it's 2.65 differential locked up in 5th gear, i'm running about 2550rpm at 95mph. With the tweaked injection pump, this has a ton of torque in the lower rpm range and is so happy. As nice as all this was, the car still needed a lot more work. The rear suspension links and bushings were shot. The differential had a lot of play from the time i got it and the pinion seal leaked. replaced pinon seal and it got fresh gear oil, no difference. The body was also in poor shape. a few hail dings, rust under rear door seals, had mismatched hood when i got it because it was replaced from hail damage and planned to be painted but i swapped for another mis-matched 1995 hood. Paint itself was sad on the roof. I also think the roof rack leaked too. Well anyways, i recently picked up a 1991 300TE with no engine. The guy i bought it from is an automotive fabricator that was going to put some Chevy LS engine in but was too busy with other projects. He got it from original owners when it overheated and it was going to cost too much to fix. Cali car, white paint, blue interior. body is nearly perfect except the hood paint. BUT... i have a white 1995 hood that i prefer the look of anyways. The interior was also blue in my "old" wagon so i have some good parts there along with a black dash i installed. Shortly after buying it, my Differential blew up on the highway. i think may have been due to the pinion seal leaking but i knew it was not happy. Picked up another 2.65 for the TE with no play!

I have completely torn down the TD for all parts that will be needed for the conversion and will be keeping it around until i am sure i have every little washer, ect to make this a perfect swap! There is a lot of wiring differences i will have to work through. Once the large "diesel" harness was carefully labeled and removed, i still see a few differences in wiring that i'll have to sort out. The 91 has a TON of improvements that i am really liking so far. looks like way more insulation is used everywhere, door midbass drivers, auto down front windows, the later wiring for power seat switches, ect. I have a TON of pics of all upgrades but i'll just post some of the overall idea ones haha!

More pics. the new white wagon and parts being removed from the TD!

Oh and a PARALLEL FLOW condenser going in the new one! Should be great with R12 :D

How? Where? What?

Where did you get the differential! I WANT THAT KIND OF GEAR RATIOOOOOOO! :eek:

Stock for 603 powered W124's. But the 722.6 5 speed auto i installed has an overdrive 5th gear and locking torque converter :). I believe the E420's got a 2.24 differential but would impact acceleration and cause your torque converter to produce a ton of heat.

I am very interested in what it took to fit the 722.6, and what it took to make it shift & lock up properly.

Great project, many have considered moving a 603 or 606 into a gas chassis. My choice was going to be a '94/'95 wagon, for the final body/chassis/interior upgrades, but it looks like you have most of that already and will be avoiding the later integrated harnesses that the M104 cars have.

Please let us know all that you run into making the change, and of course what it took to make the 722.6 transmission work on the OM603 in an early body!

It took a bit of work to use the 722.6. A lot of little details that added up to make it as "factory" as possible with all MB parts from W124, W210, and R129. I also play with the settings on Ole's controller quite often. I absolutely LOVE being able to adjust every single detail on the fly and even save different shifting maps that i can select from the W/S switch. It also supports VGT control which i hope to use, idle control and adjustable speed via the ELR, and a ton of inputs for more accurate speed calculation, ect. I have to say Ole has been a huge help with all my questions regarding software and hardware. He has made an absolutely wonderful controller and is releasing updates often. When I re- install everything into the white wagon, i'll be sure to take some better pics of everything.

Got further on wiring tonight. Removed the gasser engine bay wiring harness. Now on both gas and diesel harness's, they have a large plug in the fuse box that goes into the interior. i assume this carries signals like temp, oil pressure, tachometer, a/c compressor to klima system, and more. does anyone know where to find the pinouts for both the 91 and 87? I just want to make sure pins aren't swapped around for some reason and the coolant float triggers the glow plugs or something! :D Also the gasser had another 3 pin connector along with the large plug. I assume this is maybe for the fuel pump relay? I am pulling the dash and probably the seats and carpet for a proper cleaning and to also remove more gas spec wiring like the fuel pump stuff and lay all my stereo wiring in place. I also removed the brake pedal assembly with all the cables that locked the shifter and will be installing the 87 on in it's place with my 400e brake booster. had to remove that to pull wiring looms out. Does anyone know if it would be worth it to sell that under hood harness. I removed it very carefully and the only wires that are cut are the ones for the wiper nozzle heaters! It is a pretty big harness too. Just curious.

The electrical manuals can be found at

Model 124 Maintenance Manual Index

Chapter 24

Be sure to look at the drop down and get the extra pages that were left out, you will need them.

This print deck covers 87 to 93 so you should be able to cross check the various systems.

One difference I know for sure is the climate control and the aux fan. 87 used a thermal switch in the head direct to the relay. 88+ uses a thermistor in the head to the CCU to drive the fan relay.

Someday I hope to do something like this to my 87 so be sure to make lots of notes about what you find!

While the interior is out, a great time to install the wiring for the '94/'95 power driver's mirror.

Are you still running a cable speedometer with the 722.6 or is this transmission electronic speedo only?

The speedo on the 210 is electronic. It pulls data from the power train CAN bus and drives the stepper motor in the cluster.

No cable hookup on a .6 as far as I know. I wonder if they even use the transmission in the 210s for speed, they may just get it from the ABS sensors. I know the car can't stand different sized tires on the front and back, it drives the computer crazy and won't allow the cruise to engage.

No speed cable in W210. The cluster gets the speed from the rear ABS sensors (only). The speed sensor in the conductor plate is only for the TCU to use. Later W211 and onward started to use a combination of conductor plate speed sensor and ABS sensors to calculate the real time speed. You are correct that W210 TCU is horrendously sensitive to different sized tires. The tolerance on tire size difference is "supposed" to be 5%, but in practice, it is much less than that.

Hell, if the rear tires is deflated enough, the ABS and TCU goes crazy.

Good idea on the power passenger mirror, i think a pick n pull has a 95 w124 for a donor. The controller drives MB electronic speedo's. I am using one i got on ebay for a late model e420 w124. The controller has adjustments for speed compensation as well for things like different tire size, diff ratio, ect. It actuall calculates speed by the different moving gears in the trans as there is surprisingly no "final output" speed sensor. It does a great job in calculating speed but sometimes hiccups and throws it all off. But no worries, you can tap into something like the rear diff ABS sensor for a reliable speed source! The controller has lots of inputs you can configure for things like that. now remember the original harness to the 722.3 NSS has to be modified and a new one soldered up that will be in the interior. The shifter itself has the switch for reverse lights and if you'd like the controller can drive a relay to control starter lockout.

Got any spare blue wagon interior bits you'd be willing to part with?

yeah a handful, just depends on what you need.