1993 600 SL one cylinder misfiring

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1993 600 SL one cylinder misfiring - 2/14/2005 9:11:53 AM    CRC 1993 600SL   Posts: 8 Joined: 2/14/2005 Status: offline Hello to all, I have just recently purchased a 1993 600 SL in Switzerland, the car sat in a dealers showroom for almost two years before I bought it (I bought the car in Italy and exported it to Switzerland, it seems not many people in Italy appreciate such a gas-guzzler... ) and it had several problems due to it being inactive for such a long time; the brake pump and the suspension pumps had both started leaking due to the rubber components inside beeing cooked by lack of use and I had to change both. The hydraulic suspension system was ridicously expensive to change (over 3000 €) but MB does not offer a rebuild kit! I finally managed to change all these components (as well as the engine bay lining that was cooked by the engine heat) and my mechanic tried it out... it worked very well for about five minutes and then the last cylinder on the right side of the motor started misfiring! He then proceded to check the wiring harness which was badly damaged (it's cracked, probably by heat). He then proceeded to bypassing the damaged part of the cabling but the problem still continued (works OK on cold, after 5 minutes goes back to 11 out of 12 Cyls). He tried to invert the electronic boxes (left to right) but the problem reappeared again on the same identical cylinder (therefore it would not seem to be related to the electronic side). Changing the injector does not change the symptoms (still the same problem). We are now in the process of ordering a new cabling kit but given the tests that we performed it will probably not solve the issue (we tested by connecting directly the central electronic box to the injector bypassing all the cabling and the problem still arises...). Any suggestions on what it might be? I'm starting to get depressed (I've owned the car for two months now and used it only for one week!) Thanks, Robin Post #: 1

RE: 1993 600 SL one cylinder misfiring - 2/14/2005 1:42:36 PM    A Dalton   Posts: 59 Joined: 1/16/2005 Status: offline Take a compression test warm on that cylinder and swap the plug Bosch F8DC4 only.. Simple diagnoses would be to get an ignition scope pattern on that one.. < Message edited by A Dalton -- 2/14/2005 1:43:54 PM > (in reply to CRC 1993 600SL) Post #: 2

RE: 1993 600 SL one cylinder misfiring - 2/14/2005 1:59:12 PM    CRC 1993 600SL   Posts: 8 Joined: 2/14/2005 Status: offline Thanks. I will forward to my mechanic and see if he can do it tomorrow (it is 20:00 here now...). In the meantime I have received feedback from further testing: My mechanic connected an LED to the injector (in parallel) to see what happened. This is the pattern: Cold engine: Turn the engine on. Works on 12 Cyl. Led blinking each time Cyl n° 6 Right bank fires Engine warmed up (roughly 5 min on idle): Motor working with 11 Cylinders. Led is constantly off (injector is closed) will update if compression test on warm gives weird results... Thanks, Robin (in reply to A Dalton) Post #: 3

RE: 1993 600 SL one cylinder misfiring - 2/14/2005 11:48:15 PM    TheV12pwr Posts: 91 Joined: 8/28/2004 Status: offline Just wonderin'....how mugh did you pay for the car??????? _____________________________ DRIVE IT LIKE YOU STOLE IT! (in reply to CRC 1993 600SL) Post #: 4

RE: 1993 600 SL one cylinder misfiring - 2/15/2005 2:46:29 AM    CRC 1993 600SL   Posts: 8 Joined: 2/14/2005 Status: offline Paid 25.000 US$ for it (has about 40K Km on it) but already spent over 8.000 US$ on repairs and spares, I also had it resprayed, since the owner never used it with the top down the paint was much lighter (sun exposure) on the outside of the car compared to where the hardtop was sitting (when open you could notice the shiny new paint where the top began and it looked horrible...). So I could say that the total cost, up to today, was in the region of 33.000 US$ (but I still have to fix the Cylinder gremlin and pay for all the time it is taking my mech on this issue)... One of the silliest bits I had to rebuy was the 600 SL badges... the previous owner had them removed!!! (all except the V12 ones on the side) (in reply to TheV12pwr) Post #: 5

RE: 1993 600 SL one cylinder misfiring - 2/15/2005 2:53:19 AM    CRC 1993 600SL   Posts: 8 Joined: 2/14/2005 Status: offline I also forgot to mention I had a new performance pack installed (extra power and torque) which cost me an extra 1000 € approximately (I can get more precise info later today once I get to the office)... I was also thinking of getting new wheels (18 inch maybe) but I'm still in the process of evaluating the option, any suggestions? (in reply to CRC 1993 600SL) Post #: 6

RE: 1993 600 SL one cylinder misfiring - 2/15/2005 8:27:35 AM    CRC 1993 600SL   Posts: 8 Joined: 2/14/2005 Status: offline As promised here are the performance pack details (European model): Original HP 394 hp New HP 418 hpv Original torque 570nm New Torque 661 nm Speed: Old: 250 Kph New: 300 Kph acc . 0-100 km/h Old: 6.1 sec New: 5.9 sec (in reply to CRC 1993 600SL) Post #: 7

RE: 1993 600 SL one cylinder misfiring - 2/15/2005 11:11:52 AM    bobterry99   Posts: 126 Joined: 1/19/2005 Status: offline I wonder if your mechanic effectively bypassed the original wiring to the injector, Robin. I would measure the resistance between the conductors which attach to the injector at the injector (key off). I'd measure with it cold and then hot. You should only measure very high resistance. If there is a short in the wiring due to bad insulation -- and I'll guess there is -- you will get a very low reading. (in reply to CRC 1993 600SL) Post #: 8

RE: 1993 600 SL one cylinder misfiring - 2/15/2005 11:41:33 AM    CRC 1993 600SL   Posts: 8 Joined: 2/14/2005 Status: offline I just spoke to him, he confirms that the cabling is very badly corroded and insulation is unsure. We ordered a new wiring harness which should arrive in a couple of days and will try that to see if it solves the problem. Connecting directly from the pin to the injector seemed to solve the problem earlier today but my mech says the wiring is in such a bad shape that working on it, as it is, is a waste of time since it might short circuit just by touching the cables. We agreed on waiting for the new cables to come in and try again. I'll keep you updated... (in reply to bobterry99) Post #: 9

RE: 1993 600 SL one cylinder misfiring - 2/15/2005 1:47:01 PM    Lugnut Rest In Peace 5/7/06 Posts: 3786 Joined: 12/31/2003 From: Georgia, USA Status: offline What did you do to gain 24 hp? _____________________________ '95 SL600, Black '70 Chevelle SS454, Red, real LS5 '55 Bel Air, Black, 350, 4-spd, 9" Ford '01 Corvette Coupe, Mag Red, 6-spd '03 Silverado 2500HD 4x4, X-cab '77 Jeep CJ7, Rust Bucket '03 John Deere L-120, Green (in reply to CRC 1993 600SL) Post #: 10

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