There are two coil pack for the sparking plugs situated on the front of the engine behind the radiator.
They are positioned in such a way that it is extremely difficult even to photograph them let alone touch them.
Situated between the two packs is a support which hides the Number one coil pack Coil Pack the coil marked 1provideds the spark to plugs 1 & 2 Coil pack marked 2 provides the spark to plugs 3 & 4
Normally the firing order on a four cylinder engine is cylinders 22.214.171.124. in that order. there is no reason to believe the Mercedes are any different. So a breakdown of either coil will affect two plugs resulting in the loss of spark to either cylinders 1 & 3 or 2 & 4
I feel sure the only way that these can be reached is by removing the air filter housing, that will allow more room and enable the mechanic to get at the coil's from the right hand side of the engine bay.
Because of the extreme difficulty in even getting a good photo it is also difficult to see how they are secured, however in day light it is possible with a mirror to see that they are secured with a 'Torx' screw, about T30. which is located in the hole centre of the coil in each case.
Yes the ignition coil's are in a difficult position easy when they are placed on the engine before installation on the assembly line . Then how about the Sparking plugs?
I knew these were in a difficult position before I took delivery of the car , so as a condition of purchase even though the car has only done just on 10,000 miles, that the plugs be replaced, this the garage did without question, and I finished up with the plugs removed. confident in knowing that it will be a couple of years before they need replacing again period of change every 25,000 miles.
I will only be possible to replace the plugs from below , space is very and it will not be a 5 minute job. Mercedes parts do have a special tool for removing the metal plug caps, three of which can be see above the exhaust manifold. I an aware that Mercedes Workshope have a tool for removing the caps off the plugs, although I also know this job can be done without the tool in question. But expect to find these caps a tight fit.
More room is created by removing the guard above the steering rack.
In this instance the camera has captured all four plug caps easier to get them with the camera than the plug spanner. but only needs doing every two and a half years for the average mileage driver . Not to confused with the Lambda' 02 sensor which goes into the exhaust manifold.
The sparking plugs are a single electrode and are NKG R R1 on the porcelain ,with the number BKR6EZB stamped on the metal. These were obviously made for Mercedes -Benz as the have their logo on them, that does not mean you will not be able to get this plug from somebody like GSF Carparts, But you would need to enquire and check Mercedes-Benz parts, prices first as many of their parts are competitively priced.