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1995 Mercedes S420, 2000 Land Rover Discovery II, 1985 Lotus Turbo Esprit
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Discussion Starter #21
what you have to do is, take the covers off and look CLOSELY with a light where the smoke is coming from ?
epiphany will strike, you'll see it quickly. it's not something that can be diagnosed with a video like that, you need to see down into the engine,
at the actual lines, components, wiring as to which one it is.
In my original comment with the video I literally said I did all that... I took the engine covers off and inspected the entire area with a flashlight. I saw absolutely nothing that could have caused all that smoke. And then I ran the engine again and the smoke didn't return. No 'epiphany', unfortunately.

Others in this thread have mentioned the fuel pressure regulator as a possible culprit, as the engine is running rich with a strong smell of gas in the exhaust. Not sure if that's it, because the regulator is less than a year old and was replaced with an OEM unit. No smell of gas in engine bay itself.

I don't have a scanner for this car, so it'll be going out to my mechanic on Monday.
 

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1994 s600 coupe
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362 Posts
my apologies, I meant the actual video of the area where the smoke is coming from, the moment you pulled in the driveway and were taking that video of the smoke, remove the covers while it's smoking, investigate with a light, and take that same video, at that exact moment it was smoking ?? you'd have to see where it was coming from at that moment with the covers off, the source would be evident.
just wondering, is perhaps the windshield washer(s) hoses leaking onto the engine there with the hood closed, were you using the washers ?
a scanner is the first thing you should do with any modern car equipped with OBD2. good luck with the diagnosis. I have head oil leaks come and go like that. but if you have a rich gas smell, look there first, unless of course it's stuck in open loop and the coolant temp sensor/02 sensors are acting up, then yes you will get a very rich smell.
 

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1995 Mercedes S420, 2000 Land Rover Discovery II, 1985 Lotus Turbo Esprit
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Discussion Starter #23
I was thinking perhaps some wet leaves got in there; it had been raining overnight and I had to clean leaves off the car before I got in that morning. Otherwise I don't really know. Definitely nothing looks burned back there, and no obvious leaks that I can see, but it's possible I missed something.

I do have an OBD2 scanner for my other vehicles, but this one is a 1995 so it's equipped with OBD1. I need to bring it to my mechanic for him to run the diagnostics.
 

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1994 s600 coupe
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362 Posts
did you check under the dash for an obd2 connector ?
the 1992-95 is actually obd2 just not univeral like later years,
as you know it has the proprietary 38 pin MB connector under the hood.
it still is basically OBD2 because it has live datastream information,
just a non-standardized version.
actually the MB system gives a little more information than the generic 96-up OBD2 system does.
OBD1 was very primitive, and had no live data. it was a shot in the dark,
and voltage readings had to be be taken with a voltmeter and probes at the various sensors.
it was basically just a code reader system.
when your mechanic hooks up to your car, he'll get live data voltage, %, angle degrees readings for every sensor,
just like OBD2.
it's just the interface that's different, it's a slower, early analog version of the later OBD2 digital system.
 

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1995 Mercedes S420, 2000 Land Rover Discovery II, 1985 Lotus Turbo Esprit
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Discussion Starter #25
Update -- The car was sent to the shop yesterday, and my mechanic is reporting that there's no spark going to the ignition system. He swapped out my ignition control module with one he happened to have in the shop but that didn't fix the issue, although he can't guarantee that unit was good.

He checked fuel pressure and that was fine (as I suspected) so it's definitely an ignition issue.

Tomorrow he's going to investigate further. It's unlikely both coils went bad simultaneously, but we'll see what he comes up with.
 

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1994 S500 Coupe
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581 Posts
Not saying the mechanic sucks by suggesting this, but I wonder if he checked the infamous base module fuses. I'd imagine he did since he's a mechanic and all.
 

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94 - S500 Cpe
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Tomorrow he's going to investigate further. It's unlikely both coils went bad simultaneously, but we'll see what he comes up with.
Been following this thread . . . it's one or both of the coils . . that would also explain the smoke . . .
 

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1994 s600 coupe
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while diagnosing the various little issues on the M120 V12, a few times I forgot to plug one coil wire back into the coil. mind you this was only ONE coil wire for one side. the car cranked and cranked but would not start, as if it shut off spark to both banks, all 12 cylinders. I never delved into WHY that happened, just plugged the coil wire back in and it would start right up.
a complete ignition system inspection is in order for your M120. check all the wires, caps, rotors, ignition modules, wiring harness/plugs to the coffin box and ignition modules. pull all 12 spark plugs. pull all the fuses out of the end ecm in the coffin box (one of mine was blown there, causing ASR light to stay on). pull all fuses out of the drivers/left side fusebox - mine also had 2 blown fuses there, and many corroded fuses, actually MOST of the fuses were corrodes with white film ! I hand sanded every one with a small file. a disposable fingernail file will also work. spray the fuse sockets with electrical cleaner, and carefully clean all the fender and radiator support grounds, there are at least 4 or 5. sand each one and also the area they bolt to. pull all the connectors apart and carefully clean the pins and studs on the the various coolant temp sensors, and the harness plugs for the entire ignition system. pull all the plugs off the ignition modules and clean them with light sandpaper, many on my car had a layer of residue inside the round plugs, I rolled up sandpaper into small rolls and put it inside and turned it to polish them clean. these cars sit a long time, they are now a quarter century old, and the connectors are all corroding slowly. after I did all this various systems on the car were "waking up", the more I cleaned, the better it ran. and I'm still not done. check your coolant temp plugs for both sides, because if the coolant temp signal is way out like -150 F. or something due to being defective, the computer won't know how to fuel or time that parameter and may cause a no start. you have to nurse the car back to running again, and get it on a live datastream info scanner, and read all the sensors. my car had 2 very corroded dist. caps and rotors, and one cap had the center stud burned clean off and stuck in the coil wire, and it had one bad coil. clean all those small wire terminals on the 2 coils, 4 in all. clean the main coil wire contact inside the coils, where the coil wire plugs in, one of mine was corroded but the coil was bad anyway, I replaced the coil used and fixed it. just rambling on here what comes to mind based on my experience with mine, good luck with your repair, you'll get it.
 

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1995 Mercedes S420, 2000 Land Rover Discovery II, 1985 Lotus Turbo Esprit
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Discussion Starter #29
Been following this thread . . . it's one or both of the coils . . that would also explain the smoke . . .
Yep. Just heard from him, both coils. Being replaced now.
 
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