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W126 1990 500SE (ASR) & W126 1991 300SE
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Discussion Starter #1 (Edited)
I decided to change the plugs, wires, distributor cap and rotor arm on my 1990 500SE. As many of you will alredy know, the ignition wires are not available as a ready-made product from Mercedes, and so the component parts need to be ordered, and then the cables can be made up as needed. In order for the job to be done properly, you will either need the special crimping tool made by Beru (000 589 55 37 00), or will need to find a dealership that has the tool, and can make the wires up for you. The dealer I use was kind enough to let me borrow theirs, as I wanted to tackle this project myself. Actually it's still possible to purchase the tool new, but the price was around £350 which, unless you're planning a new career in crimping, is an unnecessary expense.

Special tool:
20200320_105354.jpg 20200320_105400.jpg 20200320_105410.jpg
Here are the other parts you will need:

ItemPart #PriceQtyTotalTotal + Tax
Ignition Line (Distributor to Cylinder)110 159 18 18£3.458£27.60£33.12
Cable Sleeve (End of Cables to Connectors)000 159 14 38£1.6518£29.70£35.64
Suppressor Plug (To Spark Plugs)000 156 59 10£29.708£237.60£285.12
Cable Connector (Ignition cable to Distributor)000 159 28 42£7.109£63.90£76.68
Cable Connector (Ignition cable to Coil)000 159 29 42£11.801£11.80£14.16
Cylinder 1 Tag116 159 01 37£0.852£1.70£2.04
Cylinder 2 Tag116 159 02 37£0.852£1.70£2.04
Cylinder 3 Tag116 159 03 37£0.852£1.70£2.04
Cylinder 4 Tag116 159 04 37£0.852£1.70£2.04
Cylinder 7 Tag116 159 07 37£0.852£1.70£2.04
Cylinder 8 Tag116 159 08 37£0.852£1.70£2.04
Insulating HoseN 040621 022200£2.601£2.60£3.12

The ignition line is sold by the metre, and 6.2M is what will be needed for all 8 lines, but it's good to have some left over. The following parts are also needed, but are no longer available from Mercedes:
Ignition Line (Distributor to Coil)115 159 08 18£4.351£4.35£5.22
Cylinder 5 Tag116 159 05 37£0.852£1.70£2.04
Cylinder 6 Tag116 159 06 37£0.852£1.70£2.04

I was lucky enough to find the cable for the coil, but wasn't able to get the tags. If you still have the original wires on your car, you should be able to reuse them.

Here are the parts assembled:
20200320_105322.jpg 20200320_105345.jpg
Anyone hoping for shiny new rubber connectors will be disappointed! These look ley have been sitting on a shelf in Germany since before the Berlin wall came down. Mind you, nobody is going to see them, as they are hidden by the distributor cap cover.

So, I began by cutting the first wire. Mercedes lists measurements for each one:

CylinderIgnition CableInsulation
1780mm390mm
2740mm
3900mm
4900mm
5660mm260mm
6740mm
7740mm
8740mm
Total6200mm650mm

The cable for the coil should be 595mm.

One's instinct is to cut the cables a bit longer than needed, just to make sure they do not come up short. However, the resistance of each wire will be affected by its length, so I decided to start out with exactly the recommended specifications, knowing that if the first one came up short (780mm), I could use it for cylinder 2 (740mm) and then adjust for the others. As it turned out, the specified lengths were spot on. Although on the same subject, wires going to different cylinders are cut to different lengths, so that means they already will have a different resistance. So, won't that effect the quality of spark that each cylinder gets? Perhaps the difference is so tiny, as to be irrelevant? One thing is known - we must use spark plugs without a resistor on this setup. I went for Bosch W7DCO (003 159 12 03).

So, after cutting the first length, you'll need to strip 6.8mm from the ends. The tool has this measurement printed on it (see pcs) so that you can put your exposed wire against the handle to check the measurement.
20200320_110112.jpg
Then pop a sleeve onto the end:
20200320_110238.jpg
Crimp using the first point on the tool:
20200320_110358.jpg 20200320_110443.jpg

Continued below...
 

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W126 1990 500SE (ASR) & W126 1991 300SE
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129 Posts
Discussion Starter #2 (Edited)
Next, the wire will need to be crimped using the third hole:
20200320_110519.jpg 20200320_110615.jpg
Once both ends were done, I decided to put the distributor connector on first. It's vital to use some silicone grease to help with attaching the connector.
20200320_112507.jpg
I used the grease sparingly at first, but realised that putting a bit more in there made it much easier to get the connectors on. They need to be pushed onto the end of the cable, and then screwed in - 5-6 turns is enough to reach the end of the thread. Oh, and don't forget to put your numbering tab on before you put the connector on the end!! :)

I then put the plug onto the distributor cap, and laid it out on the engine to see the fit. This was also the time where I fitted the insulation sleeve for the left bank.
20200320_114745.jpg
After the cable has been fed through the insulation tube and positioned on the engine, fit the other numbering tag, and then the spark plug connector. Again use silicone grease to aid screwing the cable in, and I also like to use a small amount on the spark plug end too. This picture shows two new spark plug connectors, the top one has some grease, and the bottom shows the bone dry rubber.
20200320_114819.jpg
20200320_143006.jpg
When putting the numbering tags onto the spark plug end, they do have to travel quite a long way up the cable. The easiest way I found to do this, was by putting the wire into the holder on the rocker cover, and using that as a stopper on the tag, while pulling the cable through.

Here's how it looks at the distributor end:
20200320_143041.jpg
So, once they're all done, you can move over to the other bank.
20200320_143126.jpg
How annoying not to have all the numbering tags!!

Ok, so that just leaves the coil...
 

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W126 1990 500SE (ASR) & W126 1991 300SE
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129 Posts
Discussion Starter #3 (Edited)
So, what if you can't get the original coil cable? Can the normal ignition cable be used for this? What's the difference? I asked these questions too, and it seems that the cables are slightly different.
20200320_143941.jpg
I should probably have stripped both wires for this photo, but still...the stripped one here is the one that goes to the coil. The internal wire seems the same, but the insulation is quite different. The ignition wire going to the cylinders has a fibre in there and a soft, pliable centre. The coil line has a much stronger rubber insulation that makes the cable stiffer. It also happens to be the tiniest bit slimmer overall, but the same sleeve is used for crimping. The senior technician explained to me that the coil wire was heavier duty, because it is carrying a charge 8 times more often than each of the cylinder wires. So in theory, an ordinary ignition cable could probably do the job, but might need replacing sooner than the others.
20200320_145310.jpg 20200320_145303.jpg
You'll want to play around with the connectors on the distributor, to configure them in the neatest way possible, before pressing each one down with a satisfying click! I think this was the final configuration I settled on before fitting the covers back onto the distributor & coil. Well, you might want to fire up the engine first, to make sure it's all running ok. :)

It was a bit of a long, laborious job to crimp 18 sleeves and screw on all those connectors, but it's satisfying to know that everything has been done properly, and will not need touching again for a very long time. The car definitely runs smoother at idle, but I still have an issue with a misfire under heavy load.

The overall cost was about £450, which is a lot of money for ignition wires, but I prefer using factory parts wherever I can, after previous unpleasant experiences. Here are the other parts I fitted on the same job, taking the total up to about £800 :cry:

ItemPart #PriceQtyTotalTotal + Tax
Spark Plug003 159 12 03£8.558£68.40£82.08
Rotor Arm000 158 40 31£65.501£65.50£78.60
Distributor Cap000 158 52 02£158.001£158.00£189.60

I'll do another thread on the spark plugs, as I can hopefully draw on the collective knowledge here for diagnosing an issue with them.
 

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1991 500SEC 50K mi. 1987 560SEC Now 153K mi. 2020
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4,412 Posts
Oh my goodness... What a labor of love it seems.

We here in the USA do not have a VAT.. while each state may have a 'sales tax', here in Boston, MA it's 6.5%.

My first set of ign leads was from MB a way long time ago, back in 2004.

The second one was a couple of years ago.. Each was all complete & of great quality.
Still waiting to be installed.

I never went to those lengths you mention, by making up wires from scratch.

A very detailed writeup indeed!

MBL
 

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1986/1990 W126
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Well done. That's the way they come normally isn't it. I think I'm the States they get made up for people.

The cost of these is bonkers, but they're the only ones I really want. I managed to find someone selling a new set, already put together but it was from Australia ages ago now. Worked a treat.
 

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W126 1990 500SE (ASR) & W126 1991 300SE
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129 Posts
Discussion Starter #6
Thanks Guys. Yeah, I would have happily bought them ready-made from MB, but no luck! Thankfully they're still doing them for the M103, but not the M117.
 

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1990 SEC
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4,146 Posts
When you have a tool with a "Made in W Germany" stamp you know you've got the real deal and not a cheap Chinese copy.

Gotta love >30 year-old spanners.

Some years ago I started using Griot's Vinyl & Rubber dressing on old rubber parts that are NLA. Not a cure-all, but seems to help prevent further deterioration.
Vinyl and Rubber Dressing - Griot's Garage

2625531
 

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W126 1990 500SE (ASR) & W126 1991 300SE
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129 Posts
Discussion Starter #8
Unfortunately that Griot's doesn't seem easily available here, but if I see it I'll definitely give it a try.
 

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04 odyssey (265k) 1995 E320 wagon (295k)
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I leave old rubber bits in that stuff in a plastic bag like a bath while doing projects Lol. Seems to help. Better than shite uro rubber pieces.

Nice job on the wires!
I went the easier route..we'll see about durability. They use bremi components, and correct connectors. Fit my early (83) 500se, except for the coil wire...it's longer than it should be.
Bremi-STI Karlyn/STI 113G/8
 

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1991 500SEC 50K mi. 1987 560SEC Now 153K mi. 2020
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4,412 Posts
Hey Martin,

I really like your attention to the little details... the tiny rubber numerical labels and the way your put the plug wires into the distributor cap as well

My MB wireset did not have the labels so I took them off the old wires and reinstalled them on the 'new' wireset on the 560 back in 2004.

When I went to change the cap etc. on my then 40K mile 500, I took off the black cover and saw this image. It had not been touched since new I reckon, judging by the dust in there, and the fact two of the screws were seized into the distributor.[Dissimilar metals, don't you know?]

With the new cap, I replaced each lead the way I found it, referring to my photo & the notes I took as I removed each wire in turn, replacing in reverse order.

Today, sitting here I am chuckling a bit with my somewhat obsessive nature regarding such things.

In the pic below, yours is the clean one.

Stay safe, man.

M.

Screen Shot 2020-03-28 at 10.42.54 AM.png


IMG_1376.jpg
 

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W126 1990 500SE (ASR) & W126 1991 300SE
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Discussion Starter #11
Hahaha, thanks for that! Yeah, I do also get carried away with the tiny details. Well, isn't that the main reason for doing our own work? So that we know it has been done properly. Even the best professional just doesn't have the time to do each job with such care, and let's be honest, one is unlikely to have the best professional working on their car!

So it looks like I got it pretty close to factory! Well, my 6 cable looks a bit kinked, but I'm sure I would have straightened that one up before putting everything back on. The only difference is that I snaked the coil wire underneath 8.

Thanks again for the pic, I love to know how things were at the factory. I also notice that each of the number tags are placed as close to the connector as possible. I wasn't sure of the correct placement, but I decided that I would bunch them up to appear in such a way that you could see them without having to remove the cover. Not sure why, but it seemed like a good idea at the time. 😀
 

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1990 300SEL, 2005 SL500
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Thanks Guys. Yeah, I would have happily bought them ready-made from MB, but no luck! Thankfully they're still doing them for the M103
Are you sure that the cable set is still available for the 6 cylinder?
Can you please check on it Monday? Since I have no special crimping tool nor I know one who does I was forced to look at aftermarket alternatives. Now you have lit the candle back on.
I can only imagine new MB cables in the freshly cleaned engine bay.🌛☁
 

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W126 1990 500SE (ASR) & W126 1991 300SE
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Discussion Starter #13
Plug Wire C1/2102 150 5318£26.202
Plug Wire C3/4102 150 5418£32.602
Plug Wire C5103 150 5518£32.601
Plug Wire C6103 150 5618£32.601
Plug Wire Coil to Distributor102 150 5818£26.201

This is the order I placed in summer 2018 for my 300SE. I don't know if things have changed since then, but all were available at the time. We can't check until things reopen. :(
 

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1990 300SEL, 2005 SL500
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I don't know if things have changed since then, but all were available at the time. We can't check until things reopen. :(
Sorry, I thought they would have like a local dealer site where you could check stock online.
My iPod is getting quite a workout now days. Most needs to be taken care of virtually. Even groceries. Hope this distancing will help us all.
 

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W126 1990 500SE (ASR) & W126 1991 300SE
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Discussion Starter #15
I wish there was a way of checking availability online! Someone please chime in if they know anywhere that has a parts number checker.
 

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1991 500SEC 50K mi. 1987 560SEC Now 153K mi. 2020
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Here is the link to Canadian parts search,
Sit down before you look at the prices! :mad:
Shocking!

For what it's worth: I found this also, though I have no idea where this first site is from. The price is certainly different!!

This one I am familiar with & can be a good source.

M
 

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Registered
W126 1990 500SE (ASR) & W126 1991 300SE
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129 Posts
Discussion Starter #18
Wow, that's a huge variation in prices across the 3 sites. Finally the UK has the lowest price on something!

I wonder how reliable those sites are when they say 'in stock'. Does that mean it's definitely available?
 
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