This might be a dragging post (like all my other ones) forgive me for the prolific detail, I like telling stories?


1992 Mercedes 300SD Turbodiesel


Have slowly been going through this junker 92 300SD and have been making progress. It's been running better with every little thing I do to it and it's the third rod bender parked by the house so I'm no stranger to the bender of the beams. I've got a few 3.0's hanging around in storage if this one has completely bit the bullet (the other two don't burn oil, both nearing 300k at the moment).

Anyway, the ole bender's covered 173k miles, I'm assuming original engine as I haven't crawled under the car to check for the reman tags. Doesn't leak a drop and everything is absolutely bone dry. Honestly I bought the car because it has a new trans, new injectors and it's old man tan (Impala Brown). It's too hot out to strip it down so I figured I might as well fix it up a bit and make a couple extra bucks to buy some more junk if I can sell it.


1992 Mercedes 300SD Turbodiesel


SO, with that out of the way:

Vacuum
The car is slow. Slow as in 0-60 in 10 years. Someone was playing with the vacuum system on the car and had it all wrong. It's now all entirely redone. Even got the reverse position prongs to pop up when going into reverse. No dice. Still slow with vacuum in order.

Shut off
Car doesn't shut off on it's own. Hit the key and it tries. Shut off valve holds vacuum and engages the lever perfectly. No problems there.

There's a shut off relay 0015429119 in the fuse box (if anyone is parting a W140, I'd like to buy this relay) - pulled that out, opened it and it has a blown track. Figured OK, soldered a bit of wire back in and tested the relay out. While plugging it in, the shut off solenoid make a click. Then a couple seconds in, the relay goes haywire and clicks rapidly non stop.

I check out the wiring to the solenoid and it's shot, somebody was screwing with the harness. I'm tempted to pull it and rebuild it, but it's beyond gone and someone did a hack job on it. If anyone is parting a W140 diesel, I'd like to buy your engine harness. It can be cracked too, as long as wire colors and such are easily visible and it complete. At this point I'm thinking this whole ordeal is just the harness shorted and is giving me ****. This leads me to the car being slow and having on odd shimmy.

The shimmy
At idle, if I crack open the injector lines at the injectors, 2 through 6 cause the engine to shake badly, good sign. If I crack injector #1, no change. I've found my missing cylinder, Bad sign. Fuel is getting to the injectors just fine. all injectors had a very light soot on them. I needed to replace the return lines so I pulled all the injectors to clean and adjust if needed via my pop tester - seller wasn't lying, they are new. Though, Bosch India's. All adjusted 135-140bar and perfect spray. Cool.

Prechambers were leaking some compression. #2 was choof choof choofing away while the engine was running. I only noticed them leaking because I was spraying around the area with brake cleaner to clean up before removing the injectors. Loosened the collar nuts and retorqued them. They were also fairly loose, which was odd. Hey, no more leaking prechambers, though.

Fuel filters are new. Fuel lines are good and not leaking air as best I can tell.

So now I have this miss on cylinder numero uno that I have to figure out. Luckily it's the easiest to get to. Compression testers at the other house, so if someone has one in the Chicago area I could use, that'd be cool. Don't feel like driving 6 hours for it.

I noticed the delivery valve retainer brackets aren't in place on the injection pump, telling me someone was messing about with the delivery valves. Would an incorrectly torqued/installed assembly on the injection pump cause a miss? Fuel is still being delivered and burned.

The engine has a miss up to a certain RPM range. That RPM range varies and is variable load. Once it's in the sweet spot, it runs like a damn dream! I was playing around with the wiring harness while looking at the shut off valve and I had the engine running. It seemed to smooth out immediately and had no shaking whatsoever.

Is there anything electrical on the injection pump that would cause this? As far as I know, rack position sensor is just for EGR flow, and I'm too foggy on whatever else I was looking at. My brain is infused with all things Datsun and OM617, 606 and every pre 2000 gasser engine. For some reason the 603 is the odd man out, which is stupid on my part because I've had nearly a dozen cars with this engine.

I also realized this car has a 38pin connector today. I can connect the old Mercedes HHT to the thing and see what codes come up! I'll post up tomorrow with the whole list of codes, that's going to be exciting.


Curious where you guys would start with this. I'll try and get some compression numbers in the coming days. Just to clear the air on that.

Thanks for reading/input.

__________________
Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....