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Just Picked Up an SL600 (Pics Inside)! Please Help Diagnose A Few Tricky Faults!!
Hey guys,
I picked up a black on black 94 SL600 a couple of weeks ago and have been going around in circles trying to get it on the road. When I purchased the car, I was informed by the previous owner that it would not start/run, and that he had been told by a shop that the passenger side throttle body needed to be replaced. I enjoy wrenching on cars as a hobby, and thought this might be a fun project (the previous owner also practically paid me to take the car ). After getting the vehicle home and off the trailer, I checked all of the fluids, charged the battery, and she started right up! Unfortunately, the ASR and check engine lights were illuminated on the dash. After doing a bit of research I ran across the following website detailing the rebuild of the electronic throttle actuators on the M120: http://v12uberalles.com/throttle_actuator_rewire.htm I spent the week ordering supplies, and the following weekend rebuilding the harness on the passenger side actuator. After re-installing the re-wired actuator, and following the reset process outlined in the how to, there was no change in the function of the car. Currently the symptoms are as follows: -ASR light on at all times (regardless of whether the car is hot, cold, or started with the brake pedal depressed) -Car has absolutely no power. -When the car is driven and reaches about 4k rpm, it either up-shifts in an extremely rough manner (jolts the entire car), or bounces on an imaginary rev limiter @around 4k rpm and then makes the rough upshift. I’ve plugged my Snap-On MT2500 and the appropriate cartridge (Mercedes through 01), personality keys, and cable into the 38 pin connector, and came up with quite a bit of information. I’ve put all of this information into .pdf format and then attached screenshots of the .pdfs to this post. I don’t have a lot of experience with Mercedes electrical systems, but after a quick scan of the data pulled with the MT2500, the following things pop out to me: -The ignition voltage for the DI1 side of the engine reads a fairly consistent 29.1 volts. The ignition voltage for the DI2 side of the engine reads a consistent 0.0 volts. This says to me that the engine is running on six cylinders. -The manifold air pressure difference, ignition angle, and intake air temp seem to vary from side to side. -There is a large difference in O2S voltage, canister purge duty cycle %, and hot wire air mass from side to side. -The vehicle speed shows to be 190mph while the car is parked and idling. -The LH-SFI Ref Resistance is wrong -There doesn’t seem to be any communication from the Electronic Actuators, Cruise Control, Idle Speed Control, or ASR. I’ve attached several pics of the new car after a good wash. Any suggestions from those of you with technical expertise in the R129 V12 arena will be greatly appreciated. Thanks in advance, Craig Rhyne |
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Nice car! I'd love to have someone's "throwaway" black/black SL600 anytime as a project...these M120's can be a beach, though the fact yours starts and runs is VERY good. Stay at it....
BTW, you may want to line up the SL 600 emblems on the decklid to spec... Sounds like the 'biodegradeable' wiring harness might be suspect. Check there first (underhood areas, check for insulation cracking in joint areas, etc). Thats the best case scenario. Though...I understand the M120 uses TWO ezl modules, TWO coils, one for each side. Check the one thats suspect, as well as the coil for that bank of cylinders, R&R and retest. Best of luck and least of all, WELCOME to PP! Last edited by Bondavi; 02-05-2011 at 05:19 AM. |
#3
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Agreed. The engine wiring harness ( x2) is a likely problem. Do a forum search and you'll find information. Beautiful car.
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Resistance is Futile. |
#4
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Yup. You can't really do any accurate electrical diagnostics with a 93-95 Mercedes on it's original degrading wiring harness. Pull back the insulation and I bet you'll see a mess. Its a pricey deal with the 6 cylinders, and I imagine more with the v12s. I know some folks who refurbished their entire harness but that's way out of my league.
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1985 500SL Euro w/ AMG bits 130k 1984 300SD Turbodiesel 192k 1980 240D Stick China 188k 2001 CLK55 AMG 101k 2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!! |
#5
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Also, when the asr light is on the car often puts itself in "limp home mode" to prevent any damage and force the owner to repair the vehicle. Yours is showing the classic tells of being in limp home mode. That would explain the lack of power.
Defeating the asr (traction control) permanently wouldn't be a bad idea too. I think there's some threads on it here.
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1985 500SL Euro w/ AMG bits 130k 1984 300SD Turbodiesel 192k 1980 240D Stick China 188k 2001 CLK55 AMG 101k 2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!! |
#6
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Thanks for all of the quick responses! I agree 100% that the car is in limp home mode. When the car goes into limp home mode, does it automatically shut off one bank of cylinders, or is that a potential root of the problem that I should be chasing?
Secondly, after reading a lot of the posts on the forums about ASR, the wiring harness was my first thought as well. I've checked behind the sheathing in several places and it seems to be in pretty good condition. That, combined with the fact that most of the faulty sensor readings seem to be coming from the side of the engine that isn't running (as would be expected), and most of the faults seem to be isolated to the EA,CC,ISC system, seem to (in my opinion) point away from the wiring harness. How do the systems in question communicate? if one or both of the actuators is bad, would it cause the types of symptoms described above? Remember, I replaced the wiring on the passenger side only, but my understanding is that if the plastic potentiometer has failed, replacing the wiring to it is pointless. Additionally, does anyone know how to test a coil with a voltmeter? Thanks, Craig Rhyne Last edited by craigrhyne; 02-05-2011 at 01:13 PM. |
#7
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The Mercedes dealer should be able to pull up a vehicle service history and see if/what parts were replaced on the car. The harness, for one.
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#8
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Suggest you contact user John Roncallo. He learned a lot about the M120 by successfully stuffing one into a 107 body.
From the looks of your printout, there seems to be something drastically wrong on one side, a voltage source, a control unit, sensors, or something even more exotic. But don't take my word for anything. I'm trying to keep a '75 450SL going after many years of neglect. Best of luck. Scott
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Remember, it's not just a car. It's an Adventure. |
#9
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You may have a blown fuse in the Base module. Take the cover off the module box and check. I think you have two or more problems. First you need to find out why your engine runs on one bank only. I maybe due to a blown fuse in the Base module, or bad injector wiring. Limp home mode doesn't shut down the cylinder bank. It just electrically disconnects throttle actuators, so all you have is mechanical connection to driver's side ETA only. This is for cyl 1- 6. The other side doesn't have any mechanical linkages and just idles. In addition, you would have to depress accelerator pedal almost 3/4 down to get any response from the engine. You can try to swap parts from left to right for troubleshooting.
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#10
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I just recently attended a Saturday morning tech. session in Bloomington, MN. at Feldmann Imports. Their MB Head Tech led the session and demo'd his Diagnostic Box. The box gets way deep into the electrical sub-systems (demo'd on a 2010/2011 E350). Simple test was 6 pages, full test was 21 or 22...the car has something like 47 different, but integrated, computers running in it. Anyone of them could throw a "code" that will take you out for nothing more serious than something as simple as "Low Tire Pressure" or similar "DOHs!"
Then the stories began. They varied from driving too close to a building's A/C step-down transformer (curb-side) all the way to not having a properly "sealed" plenum on top of the engine following a simple O2 Sensor check. The one simple item that was brought up (and most electrical folks know of this ALL TOO WELL...) was having a simple ground wire not connected properly or it's mating surfaces suffering from a "touch" of corrosion. I'd look into the simple fix first, then pop a "Benjamin" and a few "Jacksons" at a trusted MB dealership (ask around and listen for the best recommendations) and go for a flow-blown scan on the "freebie" - the cost of the scan will easily save you your time and knuckles and pay for itself by giving you the proper place and location of what could be keeping you from properly enjoying the fun of that R129. Good luck!
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. . M. G. Burg'10 - Dakota SXT - Daily Ride / ≈ 172.5K .'76 - 450SLC - 107.024.12 / < .89.20 K ..'77 - 280E - 123.033.12 / > 128.20 K ...'67 - El Camino - 283ci / > 207.00 K ....'75 - Yamaha - 650XS / < 21.00 K .....'87 - G20 Sportvan / > 206.00 K ......'85 - 4WINNS 160 I.O. / 140hp .......'74 - Honda CT70 / Real 125 . “I didn’t really say everything I said.” . . . . . . . . . . . . . . . . . . ~ Yogi Berra ~ |
#11
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An update on today's progress:
-Checked the 10A fuses in the DM module, unfortunately none were blown -Rebuilt the wiring harness for the driver's side ETA; Again, no change -Swapped the ignition modules; No change -I just pulled the coils with the intent of swapping them, but it appears that they are not interchangeable (pretty sure this is correct as parts suppliers seem to list two different part #s). Can anyone confirm this? Also, is there any way to test the coils with a digital volt meter while I have them out of the car? -Next step will be to swap the distributor caps and, depending on the condition, the rotors. Thanks, Craig Rhyne |
#12
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Craig,
Not sure that you have "verified" that the w/h was replaced. IMO, you MUST know that it has before you start swapping ECUs, otherwise you're wasting time and money! In my experience, re-wiring the ETAs has NOT been succesful but for only a few cases. If the Ref Pot or the "current" yoke has failed, re-wiring will do nothing to solve your problem. Get the w/h verified or replaced if not new, then have the ETAs checked . . Menu#24 gives some places that can check them. My personal preference is Beckmann Industries. Menu#24 is here |
#13
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Quote:
Thanks, Craig Rhyne |
#14
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Craig, M120 engine harness only includes injectors, temperature sensors, and camshaft solenoids. It doesn't include MAFs, but there is another harness available for MAFs, it goes from MAFs into the ECM box LH connectors. Don't worry about CAN harness it doesn't have insulation problem. You likely need starter/alternator harness. It goes to starter, alternator, oil pressure and oil level sensors. But it isn't your primary concern right now.
You can check each injector to make sure it's activated by LH modules. Touch it with the tip of the screwdriver. When you turn ignition on you should hear ETAs making humming noise. If you removed air filters and rubber intake hoses you could see throttle plates moving as you press accelerator pedal. Don't try to move accelerator cable or linkage from under the hood - it will put it into Limp home mode. Your Snap-On should be able to connect to throttle control modules? |
#15
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This may help you with getting V12 only parts cheap.
http://www.benzworld.org/forums/sale-wanted-trade-giveaway/1566146-parting-out-1995-s600.html Since you say the harness looks good, I'm going to guess ignition module now.
__________________
1985 500SL Euro w/ AMG bits 130k 1984 300SD Turbodiesel 192k 1980 240D Stick China 188k 2001 CLK55 AMG 101k 2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!! |
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