5k Ohms VS 1k Ohms Supressors

[SELfor50]

Ok........

So I had a lengthy conversation with someone yesterday who know's most MB Models back the front.

Being I've been trying to get enough parts together to put brand new leads onto the 6.9 i'm now at the point where half the 5k Ohm supressors have not come off the old leads properly (the screw in bit stuck inside) and the 90deg dist cap ends have nearly all snapped off and not un-screwed correctly. So I have new Magnecor lead and not enough ends to make new leads.

So... that led us to a conversation about why a 6.9 should have 5k Ohm's resistors and a 450 only 1k Ohm's resistors - when the ignition module thingy are actually the same module for both cars.. same ignition system.

Apparently Bosch who made the ignition system later claimed there was no real need for different resistors, but Beru who made the leads / resistors persisted that there did need to be a difference.. (I may be quoting this wrong - so don't shoot me down).

Anyway, is there any specific fact that states why I need the 5K ohm resistors for a 6.9??

And, would there be any issue with using the 1k Ohm factory Beru leads at all?

Cam.

 

[John S]

On my 1976 450SEL I always used 5K ohm resistor leads, where did the 1K ohm details come from and was I definitely using the wrong value?

 

[TJ 450]

Well, I have a set of Bremi leads for a 450 here and they are 5K Ohms. The ones off my 450SEL are 1K Ohm.

There are also leads available without resistors from the factory and those were on my Euro W126 500SEC.

I think what it comes down to, is that it doesn't matter what you use, so long as you don't use resistor plugs with resistor leads. Otherwise, you would end up with 6 and 10K Ohms respectively, as resistor plugs have a built in 5K Ohm resistor.

I don't see a problem with removing the resistors altogether for a track car, or just using resistor plugs and non resistor leads for a road car. The primary function of the resistor is to reduce radio frequency interference, as said before in a previous post.

Tim

 

[SELfor50]

Well, I have a set of Bremi leads for a 450 here and they are 5K Ohms. The ones off my 450SEL are 1K Ohm.

There are also leads available without resistors from the factory and those were on my Euro W126 500SEC.

I think what it comes down to, is that it doesn't matter what you use, so long as you don't use resistor plugs with resistor leads. Otherwise, you would end up with 6 and 10K Ohms respectively, as resistor plugs have a built in 5K Ohm resistor.

I don't see a problem with removing the resistors altogether for a track car, or just using resistor plugs and non resistor leads for a road car. The primary function of the resistor is to reduce radio frequency interference, as said before in a previous post.

Tim

Thanks fellas.

Works out, 1kOhm leads are fine. Car is running with no issues at all - and is fine throughout the rev range.

Un-fortunatly the misfire that was there is still there - so it wasn't the leads.

I was convinced it was, cause the leads were so shyte.

It's un-even and when sitting at idle is noticeable.. and even the oil pressure guage drops slightly on it.. like ..brrrrr.. drop.bbbbrrrrrrrrr drop brrrr drop drop...

Next to try will be ignition module (little silver box) and then coil..
Distributor will be the last thing that gets changes.. Due to that engine being in a car that was in an accident (front engine fan had bent back and the dizzy cap was apparrently damaged - never came with one), I have a thought it may be the dizzy. But I still don't think it is.

Another suggestion was that it may be a 'short' in the dizzy cap itself. Even though it's new - it could be jumping spark to a different point. Will investigate further and report the findings.

 

[WGB]

If you look at the pictures I took in WA - it had a damaged distributor cap as well as a set of leads.

The cap had taken a hit in the accident and was definitely damaged.

?What about mixture leanness as a cause of rough idle.

Bill

 

[abl567]

If you look at the pictures I took in WA - it had a damaged distributor cap as well as a set of leads.

The cap had taken a hit in the accident and was definitely damaged.

?What about mixture leanness as a cause of rough idle.

Bill

Or a leak in the inlet manifold?

 

[abl567]

A few snippets borrowed from the M-100 board, from the 600 section so 6.3 based

Ron B
Resistance is easy to understand if you forget any notion of RESISTANCE as in 'stopping the spark'.
The resistance is to Slow the spark as it is propagated ( for want of a better word).'
You do Not want a 'Fast Hot Spark',but rather a 'Long Slow one' to enable the fuel to burn completely which produces power and keeps the combustion chamber and plugs clear.
The resistance is therefore designed to make the spark act almost as if it were an ARC.
Multiple spark ignitions as made by MSD ,work on the principle of many small hot sparks over a longer period of time than one Big Fat spark as per normal ignitions. I believe the Fireball does the same.
When the resistance becomes too great as a result of aged components,then the spark will have a tendency to find the easiest route to Earth(instead of through to the earth on the plugs electrode) . Thats what happens at night when you observe an engine idling as it puts on a light show for you. By the way,Do that test with some one in the drivers seat,and get them to idle the car in drive with Air etc on. The more load at idle ,the harder the spark finds it to track to earth so any lead faults will show up then.

A good example of a Long slow spark can be found by shorting a Magneto ,they shoot a really hot spark almost 3/4" and it looks almost like a Stick welder.A interesting thing to demonstrate to little brothers...

Chris Johnson
Regarding the plug wires' resistance, you need to check everything in the secondary circuit. The wire between the coil and the distributor cap should have a resistor at each end, both measuring 1K. The rotor itself has a built in 5K resistor. The plug wire should have a 1K resistor at the end that plugs into the cap, and the plug end connector should be 1K. Note that there are different versions of the plug end connectors, and the incorrect versions have resistances as high as 6K.

So, not including the spark plugs, each spark path should have a total of 9K (1K+1K+5K+1K+1K).

Check each of the resistances carefully, and if you see any behavior that looks intermittant or erratic, toss that part. These parts can have small cracks that can open and close as you handle them.

Also check the plug wires themselves to be sure they are "non-resistive" wire. If the wires are still "factory", they will be the non-resistor type, but a lot of aftermarket wires are resistive.

 

[abl567]

BTW if anyone needs W9DC (non resister) Bosch plugs drop me a line, I have quite a few

 

[Styria]

Well, I must admit that I am totally confused, bamboozled and whatever - more than likely just lacking that basic mechanical and electrical grounding so essential if you want to be a "good" mechanic.

Again, I speak only from 'hands on' experience and what Mercedes tells me what to do - to hell with 1 ohm suppressors - get the fives even though they're a bit harder to come by. Also, don't buy the suppressors that have a 'spiked' internal fitting. I believe they're made by Bremi and I have been told countless times that they're 'rubbish' - not my words, but others. So, buy the suppressors that have the 'threaded' fitting. If you're making up leads, you will need the brass fittings that the suppressor end of the lead is crimped on. In addition, WUERTH AUSTRALIA have the correct high tension leads - I can get you those if you want them. Please don't use 'normal' carbon leads - again, I have been told many times that they must not be on a Mercedes - don't know the reason why, but I simply don't bother.

Cam, you're uneven running could be any number of items - firstly, you could consider putting a tune-up machine onto your engine to get some of the required readings. That might help. Also, take the car for a brisk five kilometer run and pull out the plugs - their colours should point you in the right direction. Also, I use platinum plugs - the difference in burning characteristics compared with normal plugs is staggering. Even two months of driving, yes two months, will still show up any wire brushing that I have used to clean Platinum plugs. Try some of those things first. Regards Styria

 

[SELfor50]

Well, I must admit that I am totally confused, bamboozled and whatever - more than likely just lacking that basic mechanical and electrical grounding so essential if you want to be a "good" mechanic.

Again, I speak only from 'hands on' experience and what Mercedes tells me what to do - to hell with 1 ohm suppressors - get the fives even though they're a bit harder to come by. Also, don't buy the suppressors that have a 'spiked' internal fitting. I believe they're made by Bremi and I have been told countless times that they're 'rubbish' - not my words, but others. So, buy the suppressors that have the 'threaded' fitting. If you're making up leads, you will need the brass fittings that the suppressor end of the lead is crimped on. In addition, WUERTH AUSTRALIA have the correct high tension leads - I can get you those if you want them. Please don't use 'normal' carbon leads - again, I have been told many times that they must not be on a Mercedes - don't know the reason why, but I simply don't bother.

Cam, you're uneven running could be any number of items - firstly, you could consider putting a tune-up machine onto your engine to get some of the required readings. That might help. Also, take the car for a brisk five kilometer run and pull out the plugs - their colours should point you in the right direction. Also, I use platinum plugs - the difference in burning characteristics compared with normal plugs is staggering. Even two months of driving, yes two months, will still show up any wire brushing that I have used to clean Platinum plugs. Try some of those things first. Regards Styria

thanks for the advice peoples.
I'm going to try swapping back to the 5k Ohms old leads I have.
Then double check dizzy cap make sure it's not shorting in there.
Then I'm going to turn to mixtures also. And double check the inlet manifold also.

Haven't had time last couple days, but will concentrate on it this weekend.
It is a little annoying, cause it was running so smooth for the first week or 2... anyway, will sort it.

Cam.

 

[SELfor50]

First things first though, I have swapped back to the 5k Ohms leads. I've noticed that since swapping to the 1k Ohms leads underneath the back of my rear bumper it was farkn BLACK, and i'm talking really black. So alot of un-burnt fuel going out.
Then under load the car sounded like it was missing sort of. More like a 'farting' sound. : :-\
Since swapping back this morning, under load it seems much better. But on idle the un-even miss is still there.

I tried the sensor flap thing this morning...as suggested by Koan from the other site. For a really really slight movement the rev range doesn't change at all (I mean really light touch) a little bit past that and it drops the revs. I didn't have a magnet, but I was able to just pull it up slightly with th emiddle nut. And it dropped a bit too.
Car wasn't warm though, this was first thing this morning. Will try again with a warmed up engine tonight.
Will probably adjust the mixture a little bit richer anyway, to see if that works.

Main thing is though, I think stick with the 5kohms leads for an M100, it does make a difference.

 

[SELfor50]

Finally pulled my finger out and did a few things this morning. I think there was a collective of a few things causing it.
I put the timing back to only 5deg advance (was at about 10deg, maybe even a little more).
I warmed it up.. and the miss was still quite clear. Tried the k-jet flap thingy... pushed it and with a tiny bit of a push (just a tap) it increased the revs.

No i'm pretty sure I adjusted the right way, I turned the mixture screw clockwise??! After doing about a quarter of a turn as suggested, when pressing on the flap then it would sightly drop the revs. Does that sound right?

Idle is back to quite smooth, still the tiniest hint of a miss - but nothing like it was.. previously you'd see the OEL pressure guage even drop as it hit. I'm in at work now, but will do another quick adjustment when I get home this arvo.
The rev range accellaration is back to smooth as now.

I will probably end up trying the 1k Ohms leads back on and see what the result is now. The difference before was probably amplified by the other issue(s).

Will double check the coil polarity too, but pretty sure they're all good.

 

[John S]

Changing the resistance in an ignition circuit changes the timing very slightly.

 

[Styria]

Hi Cam, sounds as though you're 'pretty close'. Don't forget, there can be a number of factors that could cause an uneven idle. I mean, you can really chase your tail and spend absolute 'heaps' in trying to perfect running characteristics. What I can't understand is why you would want to switch back to 1 ohm suppressors when the 5's seemed to effect such an improvement. BTW, are you using carbon or silicone leads, or orig. Mercedes ?

If engine speeds increase when pressing the flap of the 'dunny lid', it means the engine is running lean. A decrease in revs means 'rich', as would black smoke coming from the exhaust. You seem to have a good relationship with MB Spares - why not let them exercise their talents and knowledge, AND EQUIPMENT, on your car - it could save you many hours of frustration. Regards Styria

 

[SELfor50]

This thread developed due to a slight misfire in the running of the 690SE. It's now gotten worse. It seemed to go away for a bit after playing with the mixtures, but I feel i just masked the issue. So what's happened now is it's happening throughout the rev range also. After about 4500 rpms it misfires quite significantly.

Some people are probably asking why i'm revving it so high.......when in rome.

Anyway. I've nailed it down to Cylinder 5 (passenger side closest to front of the car).

Investigation so far:

Swapped lead(s) - didn't fix it
Swapped spark plug - didn't fix it (and the plug didn't look fouled)
Swapped Injector (used one from the old engine which had new injectors anyway) - didn't fix it.

I'm stumped. I was going to try and swap the fuel line but I was very close to rounding the nut on the fuel line (at the distributor end) and didn't wanna push it too far - could feel it starting to slip.

The fuel distributor is the one off the old engine as the new one had a seized middle piston as posted in the transplant thread. So I guess next step is to find another fuel divider / distributor.

Are the FD's the same for the M117 as for the M100??

Cam.

 

[B13]

I suppose you could disconnect the fuel line to the 5th injector at the injector, block injector 5 (put a cap on it), screw a spare injector into the now-disconnected #5 feed line and aim that into a glass jar.

Run the engine and observe fuel flow.

Ian.

 

[SELfor50]

I suppose you could disconnect the fuel line to the 5th injector at the injector, block injector 5 (put a cap on it), screw a spare injector into the now-disconnected #5 feed line and aim that into a glass jar.

Run the engine and observe fuel flow.

Ian.

Great fault finding technique - and i'm sure at some point down the track I will use that..

Found the fault though.. shot camshaft.

Cam.

 

[Styria]

Not good buddy. Do you have another camshaft - I have two spares. Also, how are you off for fuel divider - I have several of those, soaking in a mixture of petrol and 2 stroke oil ready for future use.

Very sorry to hear of these problems - it must be so disheartening and a source of considerable disappointment for you. I know you're young and fresh, and brash D), but surely one could do without the annoying problems you are now facing - having gotten away to such an excellent start. Keep up the chin - you'll get there. Regards Styria

 

[SELfor50]

All good, I have found a source for performance M100 camshafts. Not to expensive, just need to provide a set of second hand ones (in decent condition) to have them re-ground.
They claim they have done many of them before (race spec) and said they are a good profile.

If anyone's keen on getting some done as well, it may be good to send a bunch over so that we can hopefully get a better price. PM me for details.

Cam.

 

[SELfor50]

Turns out the issue was seized lifter at full lift.. and then as I pulled it out little bit by little bit - it wouldn't go back down.. then once I pulled it out completely I tried putting it back in, and it would hardly go in.
Turns out Inlet lifter on Cylinder 6 must also be on the blink, so swapped that too. The rocker arm on cylinder 6 was also ground. Come to think of it, I forgot to take a pic of the rocker arms.
Will do that tomorrow also.. for now, here's the other pics of today's work.

Took it for a spin afterwards.. back revving how it should and kicks on.. felt good. I think I need to wind the mixtures back a bit now, as I wound the fuel up before in an effort to compensate the misfire (it corrected it for a little while, i'm guessing cause it wasn't opening the inlet as much the extra fuel helped minimise the impact..........but yeah), so by the feel of it - I can probably have another play and get it back to how it should be.


Subject


Spares


The old engine must have had new injectors installed, so these will make great spares - removed them all from the old block.


Ian removing the new(old) cams




Removing the New (dead) camshaft


Cleared



Swapped out lifter - compare the difference between the look of the new vs old - you'd think the new ones would've been sweet? Probably just sitting idle for too long..


Kaput nockenwelle



Shot Lifter


1 More Angle of die kaput nockenwelle


Installing the backup


Burning the oil drips off the exhaust manifolds




Cam.