LJ78 Mercedes OM617 Swap ECU Questions

[Ryanwyo]

I'm working on swapping in a Mercedes OM 617 in my LJ78 with manual transmission. I'm just wondering what the ecu actually controls in the vehicle other than the injection pump and glow circuit. I'm going to use the Mercedes glow plug relay (one accessory wire to turn it on, and one wire to the starter solenoid to shut it off). And one accessory wire to run the fuel shut off solenoid. Going to run both wires from the auxiliary wiring box in the front right corner of the vehicle. For the alternator probably use the Mercedes one or a one wire Delco, then adding a signal wire to get a tachometer signal. And a starter for a 5vze that mounts to the v6 bellhousing used for the adapter plate.

Just want to know what the ecu controls such as the dash cluster, transfer case, wiring for starter/alternator, lights, and ignition key.

 

[GTSSportCoupe]

Cool swap! There was an OM617 LJ78 for sale close to where I live recently. I don't have time to comment on your questions right now, but here is the Japanese wiring manual for the LJ78. Its been translated to english thanks to @AirheadNut : '90-'92 70-Series Wiring Manual.pdf It should have the answers to some of your wiring questions.

 

[AirheadNut]

Sounds like fun! The OM617 is an epic engine when fiddled with a bit. Going from memory here, but other than the AC and tachometer, you shouldn't need anything from the ECU side of things. I'm using a couple of the wires to power the ECU for my TDI engine, but most of the engine loom on the left side of the engine bay will end up cut out. Here are some before and after shots:
The original harness:

Wires deleted:

The end result:

Most of what's left over goes to the transmission harness for the reverse light switch and the 4wd indicator switches.

 

[fjc-man]

The OM617 motor like most Mercedes diesels is actually turned off by applying vacuum to a diaphragm on the injection pump. Unlike a gas engine which is done electrically.

 

[Ryanwyo]

Cool swap! There was an OM617 LJ78 for sale close to where I live recently. I don't have time to comment on your questions right now, but here is the Japanese wiring manual for the LJ78. Its been translated to english thanks to @AirheadNut : '90-'92 70-Series Wiring Manual.pdf It should have the answers to some of your wiring questions.

Thanks! That's exactly what I was looking for. Been looking at the same ones in Japanese and that offered no help at all.

 

[Ryanwyo]

Sounds like fun! The OM617 is an epic engine when fiddled with a bit. Going from memory here, but other than the AC and tachometer, you shouldn't need anything from the ECU side of things. I'm using a couple of the wires to power the ECU for my TDI engine, but most of the engine loom on the left side of the engine bay will end up cut out. Here are some before and after shots:
The original harness:
View attachment 2201066

Wires deleted:
View attachment 2201069

The end result:
View attachment 2201070

Most of what's left over goes to the transmission harness for the reverse light switch and the 4wd indicator switches.

Did you ever get the TDI swap on the road? I remember reading you build page. Have the ac out of mine now. Don't think I'm going to mess around with fabbing the mounts hooking it back up. That will probably change this summer. Should be a good engine for the prado and some added confidence to drive more than 20 miles from my house. I've had the head off that SOB three times in the last year with two different heads. Original head was cracked, got a Chinese Quantico head that was made so poorly and out of spec it would barely run, and lastly pulled the head off a spair engine and the cam seized after 500miles and all the pistons hit the valves. Haha, would drive it for a week and have work on it for three.

 

[AirheadNut]

Not on the road yet, but I'm still plugging away at it in my limited spare time. I was hoping to beat the 2 year mark, but pretty sure I'll miss that now (Feb 22). I should have it done by early spring though.

You'll love the OM617. Any plans to tune it, or are you going to just leave it stock? My G-Wagen had Tomnik 6.5mm injection pump elements, Bosio 314 nozzles and an HX30 set to 18psi and really scooted along, even though it weighed 5100lbs. I still regret selling it!

 

[Ryanwyo]

Not on the road yet, but I'm still plugging away at it in my limited spare time. I was hoping to beat the 2 year mark, but pretty sure I'll miss that now (Feb 22). I should have it done by early spring though.

You'll love the OM617. Any plans to tune it, or are you going to just leave it stock? My G-Wagen had Tomnik 6.5mm injection pump elements, Bosio 314 nozzles and an HX30 set to 18psi and really scooted along, even though it weighed 5100lbs. I still regret selling it!

Two years is a long time. You better get after it. Haven't thought about tuning it yet. Figure I need to get it in and running first. Did you have a intercooler in your G-wagon? How were to EGT temps on the om617? I had to put a intercooler on the 2lte just to make it drivable.

 

[AirheadNut]

Mine was non intercooled, but still ran pretty cool due to the boost. As I recall cruising was 700-900F, and the highest I saw was around 1350F while hammering it hard in 3+ feet of snow. That was a fun day