R129 SL500 Distributor Advice please

[JCW1]

I have owned my 1993 sl500 for just over a year and during that time have suffered the misfire due to moisture problem that seems common to this engine.

Whilst recently cleaning the drivers side cap, I noticed that the wires that go into a two pin plug on the side of the distributor had pretty flaky insulation so I decided to sort this out. In fact there are three wires into two pins. To sort the insulation out I dismantled the plug casing and this is my problem. Stupidly, I didn't note which pin was the top and which was the bottom, although I think the two wire pin was the bottom.

Is there anyone who knows, or anyone with a similar car who could look at theirs and advise me? Is there any problem if I try both ways, is it just a case of the right way it will work, the wrong way it won't.

Grateful for any pointers.

Thanks

Chris

 

[BTB 500]

Hopefully someone will be able to help.

As you have discovered, M-Bs made in the early 90s used biodegradeable insulation on the wiring ... which breaks down. Many (most?) cars of that vintage will have had the whole loom replaced by now.

 

[Vlad]

2nd that comment re bio degradabe insulation......

Sadly I dont have an answer for you on the distributor, however, if you find that cleaning the caps doesnt work, I've just replaced the caps and rotors on my 1990 SL500 with new BERU items from Eurocar Parts at less than half the price that MB wanted. Runs like a dream now

 

[Dash1]

I have owned my 1993 sl500 for just over a year and during that time have suffered the misfire due to moisture problem that seems common to this engine.

Whilst recently cleaning the drivers side cap, I noticed that the wires that go into a two pin plug on the side of the distributor had pretty flaky insulation so I decided to sort this out. In fact there are three wires into two pins. To sort the insulation out I dismantled the plug casing and this is my problem. Stupidly, I didn't note which pin was the top and which was the bottom, although I think the two wire pin was the bottom.

Is there anyone who knows, or anyone with a similar car who could look at theirs and advise me? Is there any problem if I try both ways, is it just a case of the right way it will work, the wrong way it won't.

Grateful for any pointers.

Thanks

Chris

Hi JCW1,

I have attached a word document below with two sets of wiring diagrams for the R129 - SL500, I hope these are what you are looking for, if not, then please let me know. I have only cut part sections from the original wiring diagram with reference to the wiring colours and pin-out numbers.

Best Regards,

Dash1

 

[Dash1]

Hi JCW1,

I have attached a word document below with two sets of wiring diagrams for the R129 - SL500, I hope these are what you are looking for, if not, then please let me know. I have only cut part sections from the original wiring diagram with reference to the wiring colours and pin-out numbers.

Best Regards,

Dash1

 

[Doodle]

Just checked my pictures but none of them are indicative to be honest. Will be able to physically confirm on Saturday when I'm back with the car.

 

[Dash1]

Second Diagram.

 

[Dash1]

Hi, JCW1,

When you look at the diagrams, for easy reference I’ve identified the colours and pin-outs so you don’t get confused with them. S5/5 and S5/6 are the distributors.

T1/1 and T2/1 are in fact the ignition coils. The pin numbers and colours on both coils are as follows:

Pin number 1 on T1/1 is the ground circuit of the left coils primary winding – The colour - BK represents black.

Pin number 1 on T1/2 is the ground circuit of the right coils primary winding – The colour – BK/YE represents black with a yellow trace.

Pin number 15 is the 12-volt supply to the primary windings on both coils – The colours PK/RD are pink with a red trace.

Pin number 4 on both the ignition coils is actually the HT lead.

Note X11 on the right of the diagram which all these wires run to is actually the diagnostic socket.

Hope this is easier for you to interpret.

Best Regards,

Dash1

 

[JCW1]

Hi Guys,
Thanks very much for the replies and especially Dash1, who it has to be said, has gone above and beyond the call to help. Whilst I am no stranger to a set of spanners, I am not that good with wiring diagrams but the wordy guide at post 7 has helped. Just one thing, is a reference to 'left', driver’s side or passenger?
It is interesting to note the comments about biodegradable insulation. Before I bought my car, I did consult the indy who had last serviced it and mentioned that I had seen comments about engine bay wiring problems. He told me that the problem was related to the 6 cylinder version, not the V8!
Whilst on the subject of distributors, Vlad raised the issue of caps. With all the cars I have previously owned, a dizzy cap, even Bosch would leave change from a Tenner so I would stick a new one on, regardless of the old one's condition. With the Merc, this is not a decision to take lightly, given the cost. I believe that my caps (Beru) were replaced at the last service and do seem to be in good nick, but how can you tell if they need replacing?
Cheers
Chris

 

[grober]

Excellent diagrams DASH 1 but still doesn't tie in with what the OP describes as there are no low tension connections to the distributor body depicted on the diagram just HT . My guess would be the 2 connections with the 2 wire and 1 wire leads come from a hall effect pick up in the distributor body. In older cars [ pre- Crank position sensor] this would have been used like contact breaker points for firing the HT coils, but for cars of this age which essentially have no low tension connections to the distributor body as they are not required for ignition[ as demonstrated in the diagrams] I can only guess it used for some secondary measure of engine rotational speed/ diagnostic such as RPM counter or fuel pump relay.

 

[Dash1]

Excellent diagrams DASH 1 but still doesn't tie in with what the OP describes as there are no low tension connections to the distributor body depicted on the diagram just HT . My guess would be the 2 connections with the 2 wire and 1 wire leads come from a hall effect pick up in the distributor body. In older cars [ pre- Crank position sensor] this would have been used like contact breaker points for firing the HT coils, but for cars of this age which essentially have no low tension connections to the distributor body as they are not required for ignition[ as demonstrated in the diagrams] I can only guess it used for some secondary measure of engine rotational speed/ diagnostic such as RPM counter or fuel pump relay.

Hi grober,

Sorry, they are the only diagrams that I have for a R129 – SL500 with the 119 engines that covers the following years.

Engine 119 CFI - MY 1990 – 1992


Engine 119 SFI - MY 1993 – 1995


You may very well be right, if it does have an earlier system and its “hall effect” triggered then the wires for the hall switch are as follows

+ equals the 12 volt supply voltage.

- equals the ground circuit

0 equals the hall switching voltage - which is normally between 5 and 7 volts.

Unfortunately, I don’t have any information on those diagrams, but the system is relatively simple in construction. Maybe a photo from the OP would help in these circumstances, or, someone who owns an identical vehicle could give him guidance with the colour codes to the relevant plugs connector

Best Regards,

Dash1

 

[grober]

This is a good article. ignition problem

PS you are talking about the distributor and not the cam sensors/adjusters? http://www.w124performance.com/images/M119/EZL/rotor_failure/distributor1.jpg
http://www.w124performance.com/images/M119/engine_harness/500E_engine_harness_pinouts_1993.jpg

OP ---REALLY NEED A PICTURE!!!!!

 

[Dash1]

Hi grober,

With respect to the OP, he describes his vehicle as being a 1993 model; therefore, it can only be one of the two that I submitted in my earlier posts. The distributor caps, left/right banks are only a means of distributing the HT voltage, and nothing else. The only components inside the caps are the rotor arms; there are no electronics or components.

Only the crankshaft position sensor and the camshaft position sensors reference the triggering mechanism. The ECU itself grounds and switches the primary circuit on/off for the individual coils.

The only thing that I can think of that the OP is referring to here is the two “knock sensors” - 3 wires, they both share the same common ground wire, however, they both have their individual sensing wire circuits.

It may help if we knew the year/month of build as the circuits changed in June 1993. Maybe it would be wise for the OP to take a photo of the issue and post it so we can look further into it.

Best Regards,


Dash1

 

[JCW1]

Hi Guys,

Thanks for the continued interest. I appreciate my description might be misleading and I didn't appreciate things changed during 1993. My original assumption was that the wires were to do with a Hall Effect trigger but I have no experience with MB and no w/shop manual (yet). I will take a picture tonight and try to upload. I assume I will have to compress it.

 

[grober]

Hi Guys,

Thanks for the continued interest. I appreciate my description might be misleading and I didn't appreciate things changed during 1993. My original assumption was that the wires were to do with a Hall Effect trigger but I have no experience with MB and no w/shop manual (yet). I will take a picture tonight and try to upload. I assume I will have to compress it.

Can't remember the *. jpg limit but safe under 227KB. Just attach it with the manage attachments button below the new message box. A picture that shows context [ surrounding engine parts] as well as detail would be best

 

[JCW1]

Ok so hopefully I attach a picture to this post.

I owe you all an apology, by Googling the part number, I now know that the wiring is plugged into the camshaft position sensor unit.

 

[JCW1]

Wow, the attachment worked!!!

So I guess I just need to know if the CPS is shown on Dash's wiring diagram so that I can get the pin numbers. This may seem like a dumb question but are the pin numbers stamped on the plug shroud or the socket on the unit?

Whilst we're on dumb questions, is the rotor secured by the three hex head screw/bolts?

 

[grober]

Technically its not the sensor but the camshaft adjuster actuator magnet- this changes the cam timing [ advance/retard] to maximise torque There will be another one on the other bank inlet camshaft. Heres a diagram Y49/1 is left adjuster Y49/2 the right X26/2 is the 36 pole engine connector. You should be able to work out which connector pin is which.

 

[Dash1]

Technically its not the sensor but the camshaft adjuster actuator magnet- this changes the cam timing [ advance/retard] to maximise torque There will be another one on the other bank inlet camshaft. Heres a diagram Y49/1 is left adjuster Y49/2 the right X26/2 is the 36 pole engine connector. You should be able to work out which connector pin is which.

As grober has said, I can’t add anything further to that, that’s exactly what they are; you can now quite easily work it out from the diagram he’s provided. The connectors will have identification numbers on them, you may need a magnifying glass though, but if you can’t read them, here they are.

Y49/1 Pin number 1 - BR/GY (brown with grey trace). Pin number 2 - RD/GN (red with green trace) these connect to the multiplug connector X26/2 - pins 30 and 17 respectively.

Y49/2 Pin number 1 - BR/BU (brown and blue trace) - Pin number 2 – RD/GN (red with green trace) these both connect to the multiplug connector X26/2 - pins 5 and 17 respectively.

Yes, the rotor arm is held in place with the three screws, be careful though when removing it, they often break the lugs off the collar that holds the rotor on.

Good Luck and thanks very much to grober.

Best Regards,

Dash1

 

[grober]

As grober has said, I can’t add anything further to that, that’s exactly what they are; you can now quite easily work it out from the diagram he’s provided. The connectors will have identification numbers on them, you may need a magnifying glass though, but if you can’t read them, here they are.

Y49/1 Pin number 1 - BR/GY (brown with grey trace). Pin number 2 - RD/GN (red with green trace) these connect to the multiplug connector X26/2 - pins 30 and 17 respectively.

Y49/2 Pin number 1 - BR/BU (brown and blue trace) - Pin number 2 – RD/GN (red with green trace) these both connect to the multiplug connector X26/2 - pins 5 and 17 respectively.

Yes, the rotor arm is held in place with the three screws, be careful though when removing it, they often break the lugs off the collar that holds the rotor on.

Good Luck and thanks very much to grober.

Best Regards,

Dash1

Cheers DASH1 combined effort mate we got there in the end.