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I ordered the supposedly correct Mercedes brand spark plugs for my 2012 E550 with the M278 engine. Pert number A 004 159 81 03
I bought 9 of them,
plus a spare coil,
plus 2 spare wires,
the offset wrench
and the socket with the gimball
Then I gapped them all and started the project. It's simpler than it sounded,.. BUT,.. the plugs are all wrong !
The old plugs (which have the same markings onthe side ( Z6SII3320R) have the first thread staring across from the ground electrode,.. but the new ones all have the first thread starting where the ground electrode welds onto the plug.
This causes the plug to be indexed about 120 degrees from where it needs to be.
I checked with Mercedes and they say this is the correct part number,.. and indeed the new and old ones match numerically.
I chose to do the job myself because I KNOW no dealer or indy would take the time to do this job correctly. In fact,.. when I asked my indy (best one in the state) about he lug job and indexing,.. the tech had a blank stare on his face.
So do the correct plugs even exist?
Here's a pic of the old and incorrect new version. (Not sure why the uploader keeps rotating my pics 90 degrees. )
NOTE,.. The Bosch part number, as well as the number stamped into these plugs is the same, Zee 6 Ess EYE, EYE, 3320 (I had thought the 4th and 5th character were one's)
just did mine. got everything fcp euro. no issues with the bosch's
FCPEuro is where i got these.
The advantage of the Merc plugs was supposed to be that they WERE indexed properly,.. so you didn't have to hassle with spacer washers and such.
I need about another 1/3 of a turn to get them indexed correctly.
It loos like one turn is 0.055",.. so 1/3 of that is 18 thou.
The washers measure 0.059", so if I can find some that are 0.037", I'd be all set.
0.037" Thick,
0.655" OD,
0.468 " ID
So I guess that's 12mm indexing washers. I see they come in sets with 30, 40, 50 and 60 thousandths thickness.
I have a case of copper washers from Harbor Freight that measure 59 thou. I guess they're really 1.5mm. I see Amazon has sets of them also that are 1mm,.. which is 39 thou, almost perfect. Sometimes those are too big OD though.
I see some sets on Amazon that are 300 pieces,.. one of which is 12mm x 16mm x 1mm.
This set has 25 of those. So I guess I'll order that.
Who knew sparks where so complex, perfect detail in the pictures. have you contacted FCPEuro about a refund / correct replacement part?
*Good idea on the washer but, you shouldnt have to put your time into figuring all that out... correct part, screwed in to torque, done. FCP needs to fix this
I ordered the supposedly correct Mercedes brand spark plugs for my 2012 E550 with the M278 engine. Pert number A 004 159 81 03
The old plugs (which have the same markings onthe side ( Z6S113320R) have the first thread staring across from the ground electrode,.. but the new ones all have the first thread starting where the ground electrode welds onto the plug.
This causes the plug to be indexed about 120 degrees from where it needs to be.
Wow, good catch. I agree, I thought that indexing was critical on our Biturbo V8s.
I hope someone can chime in with an answer on the plugs.
Bosch ZR6SII3320. They were a bit cheaper than a set of OE MB ones, and when I removed the OE MB plugs, they were in fact Bosch ZR6SII3320 anyway, but with an MB logo on them. £2 a plug for an MB logo seems a bit pricey...
*thousands of an inch / mm washers ,, too complicated for me lol, multiple washers may mess with the torque specs and indexing, just buy the right part and K.I.S.S
Last edited by DjaKRAbb; Dec 14, 2020 at 11:33 PM.
It's definitely NOT FCP's fault. They just resell the plugs. And they offer a variety for me to select from.
Merc called out the specs for them, and Bosch or whomever produced them.
It's as if,... wait,.... it's AS IF, they planned to use 1mm washers on the new plugs, and changed where the threads started,.. but the new plugs still ended up with 1.5mm washers?
Could that be it?
Anyway,... for future readers,.. a 16 x 12 x 1 mm copper washer rectifies the problem.
"about another 1/3 of a turn" - come on, you cant get this far and use "about" measurements , get the right plugs and return to FCP
They're never gonna be perfectly aimed. Merc wants them within a 90 deg window,.. from 45 deg ahead, to 45 deg behind the piezo injector. Reducing washer thickness by 1/2 mm will get me within 10 degrees I think. WELL within spec.
THE BEST OR NOTHING - think about everyone else who purchases these from FCPEuro instead of the correct Bosch plugs. rip. Your washer fix sounds perfect then, nice!
So I ordered 1 mm copper washers for the Mercedes / Bosch plugs,.. AND, I bought a set of the Bosch plugs (ZR6SII3302)
The Bosch plugs go in at the same INCORRECT 8 o'clock position as the Merc ones did, despite having threads that start 180 degrees from the Merc ones (I think the thread length is a bit longer.)
Of course I had a backup plan,... a kit of copper washers in 1 and 1.5 mm thicknesses. HA !
So I break those out and try some of the 16 x 12mm x 1mm washers,... and the plugs now go in at the 4 o'clock position. WHAAAA ! How can that be?
Well, it turns out the 1mm washers in the kit are only 0.7 mm thick.
AHHHH ! Seriously !
On another note,... I have oil in THREE of the coil connectors on the passenger side of the engine. Where the heck would that have come from?
This is a bummer of a thread... As we just had our plugs changed at the MB dealer we've always gone to -- they likely just tightened them down... snug... And soon we'll be melting pistons...
I'm really getting tired of this persnickety crap - I just want to drive the car and not worry about it...
Where the thread starts doesn't dictate the position, it's where it ends and consequently the washer thickness as you have attempted to adjust.
I never had this issue with OEM plugs, we checked from time to time because I didn't believe it was acutally a thing, but I marked my socket and sure enough they were where they should be when torqued down.
The oil is most likely coming from your cam solenoids and through the harness. Check them, they will probably be full of oil in the plugs as well.
I tried two of the 0.7mm washers (0.055") and it's just above 9 o'clock.
Best I can figure,... 0.046 - 0.048 thou would be vertical.
0.050 " is a common size for dirt bikes (2-Stroke),... so in the morning I'm going to contact the power-sports store 10 min north of me and see what they have.
The oil is most likely coming from your cam solenoids and through the harness. Check them, they will probably be full of oil in the plugs as well.
Hmmm, interesting.
Yes there is corresponding oil in the harness side of the connector,.. but only in the part that goes into the coil. The outside of it where the wires enter the connectr is dry,.. as is the inside of the sheath the wires are in.
I wonder if it got there while in a previous service?
Anyway,.. I'll spray them out with some electronic cleaner and let it dry overnight.
Yes there is corresponding oil in the harness side of the connector,.. but only in the part that goes into the coil. The outside of it where the wires enter the connectr is dry,.. as is the inside of the sheath the wires are in.
I wonder if it got there while in a previous service?
Anyway,.. I'll spray them out with some electronic cleaner and let it dry overnight.
Yes, they are sealed connectors, so the oil on the inside comes down the wires and fills the connector up without leaking out. It's coming in from the pins on another connector on that engine harness and working it's way around. There are many well documented cases of that and in general it won't cause any harm, but it still indicates a leaking component somewhere on the engine bay harness that should be addressed.
The recall/bulletin just added jumper harness pieces with an isolator to keep the oil propagation to a minimum on the camshaft positioners. Didn't matter if they were already leaking, or even if oil was everywhere, as long as there were no CEL faults, install the spacers and ship the car.
So I’m curious - what are the signs/symptoms of an incorrectly indexed plug? Would the car run rough, not idle well, etc? How long until the piston melted down?
Duckstu: The oil in harness is a real deal - Ours had it - ItalianJoe1 has you covered on this. Our oil was getting into the harness at the cam sensors - it can migrate up into the ME (PCM) and to all the other sensors, coil packs, etc. Some folks aren't as lucky, catching it early, as symptoms can be multiple codes to a non-runner. Last year when our car was in for service, the MB dealer caught this, we had not had any symptoms (yet). The dealer fix is to pull the motor (seriously) and replace the entire wiring harness, inspecting all the sensors, coil packs, ME, etc. connection points for oil - and replacing anything that the oil has gotten to. I was assured that the new harness is an updated one that will not allow oil in - just this job was $10K, but they didn't have to replace any components, so they told me this was one of the cheaper ones; fortunately we still had warranty, so it was only a $50 deductible to us. Get after that oil in your harness pronto!
So I’m curious - what are the signs/symptoms of an incorrectly indexed plug? Would the car run rough, not idle well, etc? How long until the piston melted down?
X2 - I would like to know this as well, since our plugs were just changed at the dealer, which apparently doesn't automatically mean they were indexed correctly...
And thank you for that as well! I already have Torque Pro and a BT OBDII adapter - never thought to just try it and see if it works, which it looks like it should
Duckstu: The oil in harness is a real deal - Ours had it - ItalianJoe1 has you covered on this. .................................................. .................................................. ............................................ Get after that oil in your harness pronto!
Best of luck...
WOW ! THANK YOU VERY MUCH !
I just looked into 3 of my 4 cam position sensors,.. and they're all wet with oil.
The 4 cam solenoid connectors are all dry. And I pulled the two huge plugs going to the ECU,.. and they're also dry.
So it looks like I may have dodged a bullet thanks to you guys.
I'm ordering up 4 new cam position sensors now. (I don't see a kit on FCP Euro)
Seriously though,... those are just Hall-Effect sensors right ? Presumably they're a sealed unit. How does oil get out through them anyway?
Oddly,. the inside of the harness sheaths appears dry. So this is very odd.
I just looked into 3 of my 4 cam position sensors,.. and they're all wet with oil.
The 4 cam solenoid connectors are all dry. And I pulled the two huge plugs going to the ECU,.. and they're also dry.
So it looks like I may have dodged a bullet thanks to you guys.
I'm ordering up 4 new cam position sensors now. (I don't see a kit on FCP Euro)
Seriously though,... those are just Hall-Effect sensors right ? Presumably they're a sealed unit. How does oil get out through them anyway?
Oddly,. the inside of the harness sheaths appears dry. So this is very odd.
Thanks again.
I hadn't heard of this before our Service Advisor called with the news. Before you order anything - do a bit of research here. From what I read there may be some jumpers you install to keep the oil from migrating - I don't recall if you did the sensors and add the jumper/connectors, or if you can just do the jumpers. There are also some folks that detail out how they've cleaned up the oil already in the harness. Some folks have great success and others either none or they have to clean a number of times. My BIL has an E63 and they have the same potential issue - he goes to an Indy shop and that shop ALWAYS checks for this when one of our cars comes through for anything - that shop has always been successful cleaning the harness. MB doesn't even consider that something to try (I asked) - likely they don't want repeat failures, but also since there is an updated harness, I'm sure they want to install the MB permanent fix. They did replace all cam sensors btw...
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