I hear ya..
But I have the schematics for that chassis right up here and it is a simple series circuit, no doubt about it.
On the Plats . here is what has been found..
The plats have a Plat electrode , but they did not have a Plat case...so the second plugs will tend to foul after a few K miles and they don't idle well b/c of the size of the electrode.
You may have noticed early Fords w/Waste used two different Plats from the factory..one had plat electrode and the other had ground casing ..so , the car actually called for two different plugs and they has to be put in the correct cyliNders for Polarity firing difference...UNREAL.
However, that has been remedied by using the Double Plats. The IR that you use are fine..we just don't like to load the coils R factor b/c the ECU does not handle the extra load well with the series load of 2 plugs firing at once [ large gap ] and the DIS already has Resistors in both the second plug wire and the Plug connectors under each coil. No sense in putting resistors on top of resistors..unless you just like resistors ...

I will check for more info on the possible default of single fire, but all my info and 104 DIS Waste Spark suggest you are incorrect on that point.
It is Series,..check the Schematic 07..001/2 HFM/SFI -104 DIS
If both plugs arced to ground, then both coil towers would have to be Pos+ output, using one to each plug and the engine as Ground. That would make it a Parallel circuit..but the coil has definately one pos and one neg tower, making the circuit SERIES. The flow has to RETURN to the coils NEG [ ground] to complete the circuit.
Can the plug fire using the engine as a ground w/o completeing the series circuit ??? I do not see how b/c the coils secondary is isolated from any grounds... and there is NO center-tap, which would be required for par circuit.... but I will check it out...

As far as the schematic goes , the engine is not being used electrically as a ground, but rather as a connection for the base of the two plugs...and b/c that connection is the threads, the second plug has to fire from case to electrode [ out of phase with the first one]........reversed polarity.
I can see the pos side of coil being possible firing to engine ground b/c engine is grounded neg and the coils pos is looking for a neg ground, but not the neg side.. the coils neg would not be looking for a neg gound , it is looking for a pos to complete....that is where the polarity has to change and that is in the series loop design. AllData states that both gaps have to be in the circuit. We will figure it out, but regardless, the Waste is a series circuit when both are hooked up and the two plugs are out of Phase..that part is certain.

__________________
A Dalton

When you find out, please let me know. I also remembered that I have had half the coil go out and different halves on different coils and the other still worked. I agree that what you are saying is supposed to be how it works. I have just tested it enough different ways that I am pretty convinced it that it does not. I have found over my career that more than just a few times Mercedes and others are not telling the truth about how things work. I will call Electromotive next week and talk to them. They are big fans of waste spark in their systems, which is what I use.
The iridium's resistance is not a load problem because of the tip size as ngk explained it to me. The kv to fire the plug is actually lower. Otherwise I agree that double resistance is a problem.
Also back on topic. The original post was for a m103 which is not wast spark and I was simply trying to point out that the question is not as simple as yes or no. Resistance and tip size change the equation.

I have followed up with other sources and they all state Series Circuit...and polarity reverse firings.............
I will post both the schematics and the Data.
I know about the 103 engine post,...I was posting to the CTH post and agree with it....and I am also not unfamiliar w/104 sytems or electrical diagnostics.
And I would be more inclines to not believe the guys that sell the plugs simply b/c it is a known fact that most 104s run like crap with Plats...that is not me talking..it is a thousand 104 owners and techs.
But the Plug guys swear they are fine..............double Plats are fine , not standard Plats. But I am not going to get into it with plugs b/c we all have our own preferences...I am just going to agree w/CTH that the waste spark plugs fire out of PHASE by DESIGN...[ electode to ground/ground to electrode], and the internal secondary winding is a single, isolated winding feed for both , in Series.

__________________
A Dalton

Just get the Beru plugs specified for your car.

No switchover to resistor only from this European company.

http://www.kingsborne.com/

__________________
Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

Is it possible to get a set of non resistance ignition leads for a 103 engine and use the quad tip Bosch or Beru plugs. this would sort out the plug sourcing problems.
mak
300se

Waste spark engine? The M103?

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

The 103 is not a waste spark engine and I never claimed it was.

were non resiistance leads for the 103 anywhere?

Interesting - I was trying to figure out how this would be possible, and it would indeed depend on a coil producing both positive and negative high voltages. There's no other way to do it. I still don't see how it could be a series circuit the way you described it. There's no incentive for the electrons to travel past the block. They're satisfied at that point.

Arthur Dalton - I think you might have it slightly backwards. In other words, I don't think the spark travels across the block to another plug. There's no electrical incentive for them to do that. They're at ground potential at that point and it makes 'em lazy. Here's what I think is happening, using 10KV for easy math....

1) Compressed cylinder gets +10KV to center electrode. This draws electrons from the block to the center electrode
2) Those electrons have now traveled to the coil on the positively charged spark plug wire, where they become available to go out the negative end of the coil, or not.
3) The electrons travel out the negative end of the coil to the waste spark cylinder's center electrode. Because they are more negative than ground, they travel from the center electrode to the rim, where they meet ground. Circuit complete.

The reason I said "or not" in step two is because in this setup, it would not be necessary for both plugs to work in order to get one to spark, though it might make a difference in spark intensity if one were not. If the coil is producing high voltage in both positive and negative, either form of spark would be satisfied by the ground potential of the battery/chassis.

I think the reason you've got it backwards is because you're not quite correct about polarity. Electrons flow from the negative towards the positive. Therefore, a high positive voltage applied to the center electrode will cause a spark to jump from the edge electrode towards center. The opposite is also true.

Also, I think the "series" part of this circuit is in the coil, not the plugs. The two high voltage + and - taps are inherently in series........

Either way, I don't see high voltage traveling across the block and then across another air gap. Not gonna happen.


-tp

>
Of course it does.

<>

How can they be satisfied at that point...the coil secondary is ISOLATED
from any engine grounds, so it does not get grounded until it completes back to the coil...ISO CIRCUIT. It does not use or need engine ground.


And it is a SERIES circuit...no doubt about it....
Read were I state the secondary is iso from all other circuits....engine ground means NOTHING to DIS waste system. The circuit has to be completed back to the iso winding for any spark to occur.

You want a schematic????

http://www.asashop.org/autoinc/feb97/DIS.htm

< >>
No ..they are not "IN SERIES" ..the secondary winding has a + and - end to the single winding, with a tap on each end ..that does not make it Series or a Series Circuit , it simply makes it a winding with a pos and a neg side,....[ like any other dc coil winding ]...and those taps [ terminals] each feed a plug.. a pos feed for one , and a neg feed for the other...and the base of each screwed into the block... that puts the plugs in SERIES WITH the winding and out of PHASE with each other [ reversed polarity] So , no matter , the completed series circuit requires a spark jump to reach back to the coil. It is a closed loop consisting of 2 plugs and one winding.
The bases of the plug are simply mounted to the block and b/c they are both the threaded portion of the plug, that puts them OUT OF PHASE in the SERIES circuit. The second plug in the series HAS TO fire the opposite polarity than the first...if they fired in the same POLARITY, they would have to be wired in PARELLEL... and if they were in Parellel, then the taps would both have to be the same positive, using the block as negative to complete the circuit...... but they are not the same , they are pos AND neg.......... meaning we have a simple, series circuit..
You will note that my other post states that the coil does not have a CENTER TAP..if it did have one , only then could the coil have TWO pos. outputs, one for each plug..and only then would each plug fire the same polarity b/c the circuit whould then be a PARELLEL circuit.
Look up Waste Spark anywhere and you will see "SERIES CIRCUIT". where the single coil feeds plug 1, on to plug 2 , and back to the coil . ALL ISO and ALL in SERIES circuit.
Here is another one for ya.....pay attention to the engine block being used as a conductor for the seconday series flow..you are correct about the polarity, but not about the series circuit design or the plug phasing...which is the point being made.

http://www.auto-repair-help.com/automotive_maintenance/ignition_coil.php

I called Electromotive yesterday and asked this question. They verified that it is a series circuit, but could not explain why the current flows from a grounded engine. They also confirmed that the coil will fire spark plugs separately, but that the coil is not firing correctly and this will ultimately damage the coil.
I agree with tinypanzer that is must be that the negative side of the coil has more potential due to the voltage or something of this nature. I was going to try and contact someone at the university that could answer this.

I also wanted to mention that the idea of removing the resistor end on the spark plug wires and installing a resistor plug was mentioned by the gentleman at Electromotive, but that resistor wires should still be used. This applies to standard plugs though and that this is not necessary with the iridium small tip plugs. I will leave platinum out of this.

Call Eistien too..........

Fact:
104 Waste Spark isSeries Circuit and 104s run BEST with Copper Core Bosch F8DC4 or NGK equiv. ...that is not theroy ..it is years of practicle experience and it is the recommend by any Tech that is familiar with this ignition system.
And how does the guy proport for you to take the resistor out of the plug connector under the coils...those connectors ARE the resistors.

It is amasing how these threads get over the top by posters who wouldn't know a parellel circuit from a series one...

End.

__________________
A Dalton

Look, I'm not trying to be snarky here. I'm just trying to understand the circuit. I have a solid background in electronics, so please don't insult me by saying that I don't know the difference between a parallel and series circuit.


See the picture I just uploaded? That's an all tube power supply for a home stereo that I designed and built. I think my electronics credentials need no further explanation.


"It is amasing how these threads get over the top by posters who wouldn't know a parellel circuit from a series one..."

Well at least I know which direction electrons flow..... From negative to positive, contrary to your post.


-tp


-tp

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That is all you know...

...and there is current debate about that too.

It was a pleasure taking the time explaining basic circuitry to you...
Hope you got somethiong out of it.
Nice Day...

__________________
A Dalton

If you ever want a lesson in advanced circuitry, hit me up.


-tp