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1990 Mercedes 560SEL
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578 Posts
Discussion Starter #1
Okay, finally I decided not to belive in old wives tales, bit the cost and did a full diagnostics for $200 at R & H Motor Cars. They told me that it is not the catalytic convertor that is causing the problem. It is the fuel distributor cap and rotor. This has also affected the spark plugs and wires. The dealer says, my distributor cap and rotor are aftermakert products and quite worn out. The spark plugs and wires also should be OEM, it seems. Right now I have Beru wires, that are two years old. And Bosch spark plugs, that are also two years old. They have recommended that following new parts should be put in:

Mercedes Fuel Distributor Cap
Mercedes Fuel Distributor Rotor
Mercedes Spark Plugs
Mercedes Spark Plug Wires
(Finally do Lambda Adjustment)

If I do all the above, the car will run smooth, with proper acceleration. Fuel efficiency will also improve it seems. Right now the fuel consumption is 9 miles a gallon. The dealer's quote to do all the above is $1408.00. I told them I will do it myself and brought the car back with me. The only questions is, whether I should buy all the above stuff from the dealer. The dealer insists that the problems are caused by old and mismatched after market products.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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39,631 Posts
Don't they mean 'ignition' distributor cap & rotor, a fairly easy DIY?
 

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1993 300TE, 1995 E320 Wagon
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1,895 Posts
Ramesh--

Buying the parts from the dealer would be a mistake, IMHO, unless you enjoy paying a significant markup. There are plenty of suppliers who can get you OEM parts at a discount. I got an OEM Bosch cap and rotor from AutohausAZ a couple of years ago, and don't think they've changed recently. In addition, I would bet thet the dealer would not give you the correct Bosch W9DCO spark plugs (Bosch no longer makes them, and you have to hunt around for them, or have connections to their secret stash, like Teutone does). NGK spark plugs BP7ES or BP6ES are good replacements. Bosch wires are also rather suspect these days... your Beru set is likely better.

The Lambda adjustment is a bit trickier to DIY, but not alltogether impossible. An investment of $50 for a good digital multimeter, and a 3mm long-handle hex key will give you the ability to set it yourself. Check out this thread....

BOSCH KE3-JETRONIC MIXTURE ADJUSTMENT



I would give Jonathan a ring at BlueridgeMB-- he can certainly set you up with all the correct stuff, and he'll give you great advice to boot.

blueridgemb.com

You can also try AutohausAZ, Fastlane (Peachparts), BMA, or Germanstar.

Auto Parts at AutohausAZ - OEM Auto Parts - Discount Replacement Parts, Resources and Car Care Tips

PeachParts FastLane Mercedes Parts Store

BMA Auto Parts | Bumper to Bumper since 1978 | Oem auto parts, vw parts, sachs boge, mercedes benz parts, honda auto parts, saab parts

Mercedes Benz Parts, Mercedes Parts, Accessories
 

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1990 Mercedes 560SEL
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578 Posts
Discussion Starter #4
Don't they mean 'ignition' distributor cap & rotor, a fairly easy DIY?
Yes, it is the ignition distributor and rotor. I don't know why he kept saying the fuel distributor. I checked his written report.
 

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Premium Member
2012 CL550 4MATIC Coupe
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9,985 Posts
Yes, if you change all of that, the car IS going to run better by virtue of new cap and rotor. Mine were all shot and that was the first thing I did and the car jumped to life. The one thing I love about my cars is the fact that you can still get to everything without removing much. Mainly just the air cleaner. Everything is right there and all of the plugs are easy to get to.
 

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1990 Mercedes 560SEL
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578 Posts
Discussion Starter #6
ElRojo, thanks for the link on lambda. Long time back the Professor (DrewProf) and me did the lambda adjustment using an oscilloscope. Very tricky to get to the screw with the hex key.

Mclare, I am wondering whether I should also put a new ignition distributor. Does it also go bad? I know that the distributor cap is easy to change. How easy is it to change the distrbutor?
 

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1990 Mercedes 560SEL
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578 Posts
Discussion Starter #7
How long do the spark plugs and wires last? Mine are just a little over two years old. They are Bosch and Beru. Any how, one of the upcoming weekends, I am myself going to check the spark plugs and wires. (It is freezing cold out there today!)
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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39,631 Posts
Yesterday was a scorcher, 100+ temperatures here.
My mechanic changed the worn out snail / worm gear drive the ignition distributor lowers into. It's quite an involved job, and as far as I remember works in tandem with the timing chain drive. I addition, to have an expert overhaul the distributor, like my mechanic did, shouldn't be too expensive. A forum search / google should help.
Cheers
 

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Premium Member
2012 CL550 4MATIC Coupe
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9,985 Posts
Mclare, I am wondering whether I should also put a new ignition distributor. Does it also go bad? I know that the distributor cap is easy to change. How easy is it to change the distrbutor?
I really do not think that is needed. Just start with the Topside stuff and go from there. Cap, Rotor, Wires, Plugs, Air Filter (opt), and then see what's up.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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39,631 Posts
In my case, the worn snail / worm gear caused my ignition rotor to fry quite frequently.
 

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1991 500 SE
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61 Posts
Guys,

None of the rotors or caps on either my 560 or 500 have ever been changed -the 560, with high mileage, genuinely idles smooth and rocksteady at 750 rpm. What diff would a new rotor and cap make? Better performance? Also, if I do replace them, is it merely a case of swopping them out, without any other adjustments needed? I'm always keen on anything that would ensure optimum running of my V8's.

On the 500 with low mileage the idling is even smoother, except it idles at 600-650rpm in N and 500 rpm in D... that's a bit too low to my liking - would the cap/rotor change have an effect on this?
 

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500 SEC AMG Mod'd
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1,235 Posts

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2004 SL500, 1993 S420, 1990 420 SEL, 1985 500SE, 1994 Toyota Supra Aerotop
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747 Posts
If you want to know if your rotor cap is screwed, just take out out (push down on each retaining screw with a screwdriver and turn 180 degrees - it pops up) and leave the wires on, look at the contact points on the underside to see if they're fuzzy and charcoal looking. Get some 150 grit sandpaper and sand them all clean, as well as the rotor tip, rotor top contact plate and the spring on the cap that contacts the rotor.

I did this and the idle is much smoother and much more consistent! I guesss then you know it was your cap and you can buy a new one (or not!).

Don't know if this is what you should do, but it worked for me.
 

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1991 420SEL, flirting with 200k
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150 Posts
If you want to know if your rotor cap is screwed, just take out out (push down on each retaining screw with a screwdriver and turn 180 degrees - it pops up) and leave the wires on, look at the contact points on the underside to see if they're fuzzy and charcoal looking. Get some 150 grit sandpaper and sand them all clean, as well as the rotor tip, rotor top contact plate and the spring on the cap that contacts the rotor.

I did this and the idle is much smoother and much more consistent! I guesss then you know it was your cap and you can buy a new one (or not!).

Don't know if this is what you should do, but it worked for me.
You have to be careful doing this, as often I learned you end up buying the cap soon after anyways. I would just change the cap, mine needs changed right now, it idles like crap and has a very pronounced miss, this is what I get for letting the car sit most of the winter!
 

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1990 300 SEL...2000Ford Fairmont
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59 Posts
When trying to remove the spark plug boot u may find the boot is "frozen" to the spark plug terminal and no amount of tugging will remove it...do not tug hard as u will cause some tearing...I did and ruined the boot...in passing, you don't need an expensive boot removal tool if you follow this unscrewing method on all the boots...just unscrew the boot off the spark plug terminal (after removing the end off the dizzy cap) and when unscrewed, zap some WD40\Penetrene or similar into the boot and onto the stuck terminal and u can then remove the terminal by screwing in another spark plug and gently pulling on the body of the plug to free the boot off the terminal...
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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39,631 Posts
Too often in the past en extension came off the socket, so now I use a locking extension, and a spark plug booth plier. Never pull the wires.
 

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Registered
1990 Mercedes 560SEL
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578 Posts
Discussion Starter #18
Too often in the past en extension came off the socket, so now I use a locking extension, and a spark plug booth plier. Never pull the wires.
Teutone: What are these other tools? I just bought the one on top. It is for removing the spark plug, that much I know. What are the others for? I have not worked on the spark plugs of a 126. There are some good advices. Will follow them this weekend or next, when I have a full day's time.
 
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