From what I here the m110 is very sensitive to spark plugs but has anybody tried using E3 plugs. I've used them in other vehicles and had good results. Any info would be appreciated

Since so many people say not to run resistor plugs, and then you add this thread... I would avoid it. KISS.

http://www.slkworld.com/slk-r170-general-discussion/115017-e3-spark-plugs-beware.html#/topics/115017?page=1&_k=1kimxv

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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,

OK makes a good point but that is a newer engine with an entirely different ignition set up, if the plugs need more power to function properly then can't the solution be to upgrade the coil to a high output MSD or Accel coil

True. You could make all types of modifications for a stronger spark.

Ironically (I believe) the newer MB cars seem to handle higher resistance plugs than the older cars.

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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,

Has anyone changed their coil to something else with more power. It's just a standard coil but I'm not sure of the power output compared to something like a MSD or Accel high output coil. I'm trying to find out what small changes I can make that will improve the engines power and economy, I know it won't be anything I can feel but at the very least it should have a more efficient combustion.

mb:
Which M110 are you dealing with?
110.9xx what is in the xx positions?
US engine?
What is the P/N of the switchgear (ignition controller/amplifier)?

No this is a euro spec I think it's around 185hp but not sure. The ignition module is the older style(the larger of the 2 designs) it's a 85 with a 5spd. I can get the numbers you need but not sure where to look. With the ignition controller you are talking about the module mounted on the fender correct?

Those 1985 ignition controllers seem to be getting harder to find at reasonable prices. Please don't fry yours with the wrong spark plugs.

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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,

Does this engine have mechanical / vacuum advance in the distributor?

What brand of distributor?

If Bosch, does it have the same small diameter distributor cap as a 4 cyl engine?

What type of trigger is in the distributor? ( points , hall effect , reluctor coil , optical )

If Bosch, you might be able to swap distributor parts from other cars to make a hall effect , reluctor coil trigger.

You might be better off using the distributor to trigger a more modern " can buy at any decent auto parts " ignition module / coil then open up the plug gaps 0.005 or 0.010 over stock.

I'm going to have to do a little digging to answer your question but for now I know it's vacuum, not sure about it being small like a 4cyl, I believe it's a Hall effect and I'm pretty sure it's a Bosch. I'll have to look to be sure. The module is new also it cost about 400 if I remember correctly. Had to get it from adsitco.

Also are these ignition modules sensitive to changes if so then I'll leave it alone. I'm not looking to make any major changes just increase the spark a little with a coil and plugs but if it can fry the module then I'll leave it be.

I just noticed this. A friend of mine has some older ICUs but none like this despite having a few m110 cars.
http://www.benzworld.org/forums/sale-wanted-trade-giveaway/2639745-wtb-ignition-control-module.html

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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,

They are indeed sensitive to changes, and one of those changes is the coil. The coil and the driver circuit in the ICU operate together to provide an oscillating decay of the primary magnetic field in the coil during the length of the arc. A change in the characteristics of the coil may not always have detrimental consequences for the ICU, however, it has happened. If your ICU matches the one shown in the link provided by fonzi (below), it is a TSZ 8u. If it has a smooth, stamped cover it is a TSZ 4. Both are sensitive.

Given you have vacuum advance, you should have mechanical advance and not advance done electronically like early 90's MB cars.

What I'm suggesting is to dispense with the MB ignition module and coil all together and use something more common. Mid 80's SAAB / VW ( and probably Volvo / BMW to name a few ) used a Bosch hall effect distributor trigger, you could use the module and coil from one of these.

Found this

http://www.benzworld.org/forums/attachments/w123-e-ce-d-cd-td/594697d1381176466-ignition-gurus-pull-m110-ignition.jpg

If the diagram is correct for your car, you have a reluctor type distributor trigger. This is basically a low voltage AC generator where ( generally ) the falling side of the sine wave triggers the ignition module.

With type of trigger, you can use a GM HEI 4 pin ignition module ( 1974 to 85 ish ) and a remote ignition coil ( same era, mostly on inline 4 and 6 engines, however GM went back to remote coils in the early 90's on distributor based engines so they might work also.)

A high quality GM module ( STANDARD MOTOR PRODUCTS LX301 ) is about $ 35 ( generic $ 10 ) , ignition coil ( STANDARD MOTOR PRODUCTS DR35 ) $ 13 ( generic $ 10 )

The GM module measures about 1" x 3" x 3/8". The GM module needs a heat sink so don't just mount it to the fender, the the MB aluminum box would be fine and would allow you to use factory wiring.

There are some issues to tend to, nothing major.

Find the spec for GM reluctor coil resistance and compare to MB of 450 / 750 ohms just to make sure MB isn't using a coil wildly different from GM.

Research what polarity the reluctor coil GM uses and compare to your car. This can be arrived by trial and error, measure ignition timing with the MB system, make the conversion without changing the distributor then recheck timing. If it is more than 3 or so degrees different, swap the reluctor wires at the module and check again. If the polarity is incorrect, the timing will be very far off. Turning the distributor to compensate will bring the timing back but the rotor phasing relative to the distributor cap will be off. This will allow spark to jump to the wrong plug wire as mechanical / vacuum advance comes into play.

The two ballast resistors must be bypassed, current limiting is taken care of in the GM module. If this is difficult, use terminal 15 in the MB box.

For wiring I'd use pin 15 on the MB box as it is already before the resistors, also run this pin to the positive side of the ignition coil. 31 would be the ground , 16 would go the negative side of the coil. Also connect the reluctor wires to the GM module.

The GM ignition coil has a spark plug type high voltage terminal so you might need to make a coil wire.

Loss of tachometer signal from pin 10 of the MB box might become an issue as the dash might not be able to deal with being triggered from the negative side of the ignition coil. This could be a show stopper if the signal is used for other purposes like fuel injection / trans shifting / HVAC. Simulating this signal would be possible if we knew details. ( a lab type oscilloscope would tell the tale )

Your distributor cap terminal spacing dictates how wide you can pull the plug gaps open before you get arcing under the cap. The larger the plug gap, the higher the voltage will climb, this stresses everything back to the ignition coil as electricity is trying to leak out.

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