M119 Ignition issues when warm

[gsxr]

Beru rotors had been reboxed OE Genuine, made by Doduco, up through summer 2020. These are NLA, and Beru is now reboxing Facet-brand rotors, with a slightly different part number (EVL-xxxx). Only Doduco rotors are available from Mercedes. These are lacquer coated and have proper-size hex heads in the bolts. AFAICT, the Doducu rotors are the absolute best quality rotor available for the M119.

Beru caps, I don't know who the OEM is, there are no markings to indicate the manufacturer. The label says made in Germany. Detailed photos are on W124performance.com.

Several years ago I had a defective Bosch cap, out of the box. It would misfire only when hot, only at idle. I wasted hours troubleshooting this problem. Although the Bosch caps are OE/OEM, after this bad experience I switched to Beru caps (no problems, yet, as of summer 2024). Allegedly the older OE/Genuine Bosch caps had a clear lacquer (conformal coating?) on them, but they no longer have this... apparent cost-cutting. Now, the dealer caps look identical to the aftermarket Bosch caps, no lacquer coating, just twice the price. [Update - dealer caps no longer have the coating, they appear identical to aftermarket Bosch.]

Only Bosch orange insulators (dust caps) are available now, either OE/dealer or aftermarket. The old black ones you may find on early cars are made by Doduco. It might be coincidence but I've not yet encountered a failed Doduco insulator.

I would love to see photos of an original Doduco cap, to check if it had any ventilation slots, or was totally unvented.

 

[robm.UK]

... AFAICT, the Doducu rotors are the absolute best quality rotor available for the M119.

Yep, I agree. Best rotor.

Beru caps, I don't know who the OEM is, there are no markings to indicate the manufacturer. The label says made in Germany. Detailed photos are on W124performance.com.

Original manufacturer of M119 distributor caps was Doduco. ‘Black caps’.

In 1990 Doduco applied for a patent which stated that their distributor cap was susceptible to failure of the base of the resin pedestal around the central electrode, due to the high electrical energy, corrosive gases and heat. According to Doduco, this resulted in cracking of the base and the central electrode parting company inside the cap. Just like the Beru failure I described above! Doduco recommended replacing the Doduco caps every 10,000 km, while also candidly pointing out that this would increase service costs.

MB did not publish a service interval AFAIK, except that the ignition components should be inspected every 20,000 km or 2 years. Normally you should expect good quality caps to last around 50,000 km.

So did this leave MB with a quandary? I let you decide.

MB directed workshops to use Bosch instead of Doduco to address a misfire problem due to moisture. Truth is, the Bosch cap was just as susceptible to moisture, if not more so IMHO.

Shortly after, Doduco was bought out by Beru A.G.

This LINK is the patent application submitted by Doduco. See item 0004.

Only Bosch orange insulators (dust caps) are available now, either OE/dealer or aftermarket. The old black ones you may find on early cars are made by Doduco. It might be coincidence but I've not yet encountered a failed Doduco insulator.

My experience is that the insulators gradually absorb moisture (if moisture occurs inside the cap and is not controlled), causing the insulator to change colour. Arcing travels through absorbed moisture, in a radial arc. A neat fix for this is to dry out the insulator with some heat and then a coat of lacquer.

I would love to see photos of an original Doduco cap, to check if it had any ventilation slots, or was totally unvented.

Yeah, me too.

The alloy recess of the M119 is sculpted with a thinner wall section to accommodate the widened part of the base of the cap with ventilation slots. It stands to reason that the Doduco cap also possessed these vents IMO.

But the vents were positioned to allow ozone to escape but not moisture.

It’s is important, when cutting additional vents, to cut the cap deep enough so that the moisture can escape as it rises inside the cap.

 

[jsmulhollandiv]

To Revert back to an earlier discussion, I popped out the distributor caps, rotors, and shields to check to make sure cam solenoid leak hadn't increased before replacing (I wanted to go for a longer drive today). To my surprise, it doesn't appear that the seals aren't leaking at all ! (so for now I won't be replacing but i'll hold onto the seals, they were cheap anyway).

Rather it seems that there is a small trickle of oil coming out of the cam adjuster magnet (i think its the cam adjuster magnet anyway) behind the power steering pump. It runs down to the bottom of the distributor cap. I've seen an @gsxr post about it and it seems easier than replacing the cam seal behind the distributor honestly... The oil was just hidden by the plastic cover. I checked and it appears to be a small trickle from the right side of the engine as well. I think i've discovered how the oil got in there... Seems straight forward to fix but I will need to get the MB sealant and see if that fixes it otherwise, i guess i just have to replace the magnet? Has anyone encountered this issue before? Its not really a pressing problem but its definitely a source of gross caps... that and a decade of sitting there... but i digress.

 

[robm.UK]

Has anyone encountered this issue before? Its not really a pressing problem but its definitely a source of gross caps... that and a decade of sitting there... but i digress.

Yup.

See this CAMSHAFT ADJUST OIL LEAK

 

[gsxr]

It's been discovered that in many cases, re-sealing the cam solenoids may not completely cure the leak. The solenoid itself can leak from the electrical connector, or the 2 halves of the metal body which are riveted together. There is a "HOW-TO" on this forum showing a process for taking the solenoid apart and re-sealing it (LOTS of work), but even after all that, it may still leak slightly.

Given the relatively low cost, if it's a car you plan to keep, I'd shell out for new ones (along with the requisite new-style armature). Remember to only use anaerobic sealant when installing (never, ever use RTV).

 

[jsmulhollandiv]

It's been discovered that in many cases, re-sealing the cam solenoids may not completely cure the leak. The solenoid itself can leak from the electrical connector, or the 2 halves of the metal body which are riveted together. There is a "HOW-TO" on this forum showing a process for taking the solenoid apart and re-sealing it (LOTS of work), but even after all that, it may still leak slightly.

Given the relatively low cost, if it's a car you plan to keep, I'd shell out for new ones (along with the requisite new-style armature). Remember to only use anaerobic sealant when installing (never, ever use RTV).

I intend to keep so I might as well replace. Not clear on the new armature though? Sorry... I’m relatively unsophisticated when it comes to changes that have happened over time.

 

[nocfn]

The armatures are to fit the new P/N magnets. If your magnets are m119 PN you need to get the armatures and new bolts. Both are under $30 from the dealer. It is 12 minutes more to change them out. The new magnets will not fit on older armatures.

 

[gsxr]

@gerryvz just posted about this in detail, as he did the cam solenoid swap recently. If you search the forum you'll find lots of photos and all the part numbers. On the bright side, you shouldn't have to repeat this job for another 20 years...

 

[jsmulhollandiv]

@gerryvz just posted about this in detail, as he did the cam solenoid swap recently. If you search the forum you'll find lots of photos and all the part numbers. On the bright side, you shouldn't have to repeat this job for another 20 years...

Little victories!

 

[gerryvz]

@gerryvz just posted about this in detail, as he did the cam solenoid swap recently. If you search the forum you'll find lots of photos and all the part numbers. On the bright side, you shouldn't have to repeat this job for another 20 years...

Little victories!

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

"12.5 dungarees" - man, that's a lot of pants...

www.500eboard.co

Armature removal (scroll down):

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

Hi JC, Yes, I can get a socket on that remaining 13mm bolt that holds the bracket to the cylinder head, using a wobbly and a couple of long extensions. It seems that it is just a bit of an extreme angle with the wobbly, so I guess I'm going to have to find another shallower angle so that I can...

www.500eboard.co

More on armatures:

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

:update: I'm at a point where I'm having to adjust the order of some of the tasks that I have been planning to do on the car, in addition to taking a hiatus for some of the Memorial Day holiday weekend, and this week. Specifically, I had intended to change the transmission fluid NOW, in...

www.500eboard.co

And last info about armatures (scroll down):

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

:update: I'm at a point where I'm having to adjust the order of some of the tasks that I have been planning to do on the car, in addition to taking a hiatus for some of the Memorial Day holiday weekend, and this week. Specifically, I had intended to change the transmission fluid NOW, in...

www.500eboard.co

 

[jsmulhollandiv]

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

"12.5 dungarees" - man, that's a lot of pants...

www.500eboard.co

Armature removal (scroll down):

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

Hi JC, Yes, I can get a socket on that remaining 13mm bolt that holds the bracket to the cylinder head, using a wobbly and a couple of long extensions. It seems that it is just a bit of an extreme angle with the wobbly, so I guess I'm going to have to find another shallower angle so that I can...

www.500eboard.co

More on armatures:

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

:update: I'm at a point where I'm having to adjust the order of some of the tasks that I have been planning to do on the car, in addition to taking a hiatus for some of the Memorial Day holiday weekend, and this week. Specifically, I had intended to change the transmission fluid NOW, in...

www.500eboard.co

And last info about armatures (scroll down):

RESTO PROJECT: M119 / W124 / E500 Engine Top-End Refresh | Member Roadtrips and Project Journals

:update: I'm at a point where I'm having to adjust the order of some of the tasks that I have been planning to do on the car, in addition to taking a hiatus for some of the Memorial Day holiday weekend, and this week. Specifically, I had intended to change the transmission fluid NOW, in...

www.500eboard.co

you = the man. Thank you so much!

 

[robm.UK]

... I’m relatively unsophisticated when it comes to changes that have happened over time.

The definition of changes happening over time is when you’re brushing your teeth, and you look up into the mirror and spot that your face is heading south.

 

[robm.UK]

I did want to flag the fact that one of our long-time members, @500AMM of Norge, came up with this solution more than 5 years ago and it seemingly worked at that time. So I view the curent dialog and findings from @robm.UK as further confirmation of what had already been posited.

I did want to point out... hah..haha..hehe..
The vent solution for the M119 distributor has been right under the noses of you w124, 126 guys the whole time! Since 1971. By example I give you...the M117 distributor cap WITH THREE SETS OF VENTS.

View attachment 117316
Similar storey for the W124, R107.

Why on earth MB decided it was a good idea in 1989 to go with only one set of vents on the M119 distributor? I have no idea. One of the last engines to have an ignition distributor, and it probably brought untold misery to millions.
Suppose I ought to include a shot of the M119 distributor cap in all its glory: -

View attachment 117318

I now regard the M119 distributor cap design with disdain.

And where were you W126 guys on the matter? Huh? haha. I only joke.

 

[robm.UK]

For completeness, here is the solution for the M119

View attachment 117332

Note, for effective moisture dispersal the new slots should extend at least 1.5mm into the base of the cap, and cut into the black suppression cover by 1mm. See page 50 of report.

Otherwise your cap could end up looking like this: -

View attachment 117334

 

[gerryvz]

I've had my M117 (560SEC) for 18 years, in several climates (Oregon, Texas, Maryland). Never had a single whit of a problem with it relating to moisture in the distributor caps, and so forth.

Then again, I've also never really had a whit of a problem in 17+ years with my M119 (E500) in this regard, either.

FYI, the large plastic "insulator" disc for the M117 distributor has been NLA for many years. If you EVER find a decent one on an M117 in a wrecking yard, I would grab it. I have one spare, of moderate quality, but I'd love to have a couple more.

 

[robm.UK]

I've had my M117 (560SEC) for 18 years, in several climates (Oregon, Texas, Maryland). Never had a single whit of a problem with it relating to moisture in the distributor caps, and so forth.

Then again, I've also never really had a whit of a problem in 17+ years with my M119 (E500) in this regard, either.

FYI, the large plastic "insulator" disc for the M117 distributor has been NLA for many years. If you EVER find a decent one on an M117 in a wrecking yard, I would grab it. I have one spare, of moderate quality, but I'd love to have a couple more.

So,... this is the world according to my chubby finger... Not especially refined or anything. No chill filtering

This is a graph (read: picture) with some nice colours of the different states of air inside an M119 distributor in the UK. I’ve added more data points. Vertical axis moisture concentration inside distributor. Horizontal temperature of air inside distributor. Run #1 summer. #4 winter 45 mins. #5 winter 9 mins. #7 winter with additional vents.

View attachment 117902

M = Misfire

So, what do we know? Very simply, below RH of 30% nothing happens. Above 0.02 kg/kg dry air moisture concentration and RH above 60%, s#/t happens.
The graph below is same thing but color bands denoting the risk band of occurrence of moisture inside distributor. Red is medium risk of moisture in distributor, blue low... you get the idea.

View attachment 117903

So, I overlaid on this 10yr highs and lows for some States in US, UK and Norway.

There is an obvious correlation, but the relationship is not simple because moisture build up in a distributor requires a sustained period (several days) of low temps close to dew point, and a cycle of engine heat and cooling. The cycle is engine warming up, evaporation, temperature differential, condensation on inside of cap (and resultant dehumidification), vapour drive from ambient air to dehumidified air inside distributor, engine off, cooling, temperature differential, condensation on alloy head behind insulator... and the cycle continues.

But the magic is for every cycle the moisture concentration increases until saturation inside distributor.

So Maryland, Oregon and Texas are low risk, which means s#/t can happen if you’re unlucky, or you don’t change your oil regularly. Or maybe you also use synthetic base oil, which holds more moisture than mineral.

Norway has it bad. Then UK.

You noticed that moisture content rises in run #1, and other runs from graphs in my report?

Edit - I am not convinced that there is enough crankcase pressure to force vapour past the seal, even when cold. The seal is designed so that pressure behind seal forces lip of seal against shaft. The build up of moisture concentration must be due to moisture released from evaporation of existing condensed moisture behind insulator and adsorbed moisture in insulator when engine warms up. So I wish to strike the following, which incidentally also does not align with my report: -
Crankcase moisture gets past cam shaft oil seal. Cold engine. Pistons rings don’t seal as well. More blowby. Condensation inside engine vaporises. Crankcase pressure build up. Seal cold, let’s some vapour past. Moisture content inside distributor rises as engine warms up. Then after 30 mins moisture content in distributor starts to drop because seal gets warmer, lubricated more with hot engine oil, crankcase pressure able to push lip of seal against cam shaft (the way the seals are designed to work).

So the cycle is complicated. The distributor has several mistresses.

But, if you have misfire. Change you engine oil and misfire will go away for a while. Use mineral oil is better for these engines too. More regular changes.

Gerry, didn’t I read somewhere you had misfire issues in TX, and you changed the insulators? Low risk. You tipped the balance.

 

[gerryvz]

Gerry, didn’t I read somewhere you had misfire issues in TX, and you changed the insulators? Low risk. You tipped the balance.

No. I have never replaced the insulators on my car, until August 8 of this year as part of my Top-End Refresh, where I replaced ALL ignition components except for the original wires. Plugs, coils, caps, rotors, insulators ..... all replaced out of hand. Coils were original units, still working fine. Plugs -- 40,000+ miles. Caps and rotors -- same. Insulators -- original, working fine.




My distributor caps, as removed:

 

[a777fan]

This is a graph (read: picture) with some nice colours of the different states of air inside an M119 distributor in the UK. I’ve added more data points. Vertical axis moisture concentration inside distributor. Horizontal temperature of air inside distributor. Run #1 summer. #4 winter 45 mins. #5 winter 9 mins. #7 winter with additional vents.

Can you go into more detail on how the data presented was collected?

 

[robm.UK]

No. I have never replaced the insulators on my car, until August 8 of this year as part of my Top-End Refresh, where I replaced ALL ignition components except for the original wires. Plugs, coils, caps, rotors, insulators ..... all replaced out of hand. Coils were original units, still working fine. Plugs -- 40,000+ miles. Caps and rotors -- same. Insulators -- original...

Good to hear you are not plagued by the condensation-misfire problem.
I went through 4 new distributor caps in 20k miles in UK. They have come down in price, but in 2005 I was paying close to $200 per cap to MB Dealer.
I am now in the 5th year on same caps using the modification.

The BW member that I thought was you was @lxm281 posting HERE.

 

[robm.UK]

Can you go into more detail on how the data presented was collected?

The analysis data is explained in the report that I included in post #35 of this thread. A link to the report is also HERE

The data that I collected is at the end of report. Theory is near beginning of the report. References at end.

The psychrometric data for air is based on well established equations.

The second graph where I produced the three bands of risk is my ‘chubby finger’ summary of my interpretations from the report.

I overlaid coarse meteorological data on the second graph, which is generally available on the internet (Wiki etc) for various states in US and a few countries UK and Norway. This is very generalised.

 

[gerryvz]

The BW member that I thought was you was @lxm281 posting HERE.

Oh goodness gracious! Heaven forbid ! Mon Dieu !

Oh, the humanity! That is quite a shocking error!

But I can disclose that 281LXM = @nocfn on this forum. Same Banzworld refugee guy.

Because, better information & moderation here.

 

[robm.UK]

Sacré bleu! Vous parlez le français le plus fantastique!

 

[gerryvz]

Sacré bleu! Vous parlez le français le plus fantastique!

En fait, l'allemand est ma deuxième langue. Mais merci pour le compliment!

 

[nocfn]

Gerry tell's good truth! Since that post, I have replaced caps, rotors, cam seals and cam magnets/armatures.

 

[gerryvz]

Gerry tell's good truth! Since that post, I have replaced caps, rotors, cam seals and cam magnets/armatures.

I'll take the confusion / conflation of myself with 281lxm as a compliment, along with my use of French exclamations.

 

[nocfn]

I thought Gerry was Cascade! Most BW think Gerry is Rex lol

 

[gerryvz]

There is a member here named @cascade. I do not believe that Rex is a member here, but for some time he and I were jihadi leaders against BW. Rex still operates his own forum at www.benzworld.us

 

[frall]

Hallo,

I'm Frank from Germany. My English is not so good.

My Car is an W124.034 (=400 E) from 1992. I bought it 2005. Over the years the car had several problems with the idle.
A restarting problem was caused by the fuel pressure regulator (Membrandruckregler). So I would recommend to check the fuel pressure too if the car has problems like this.

 

[Spencercat]

Just another data point for anyone who got this far in the thread. I recently fixed a 94 S500 with a warm start misfire/backfire/stumble by replacing the rotors, distributor caps and using the proper Bosch F8DC4 sparkplugs. The old autolite plugs in the car measured 4.3K ohms resistance (Bosch is 0 ohmz) so my theory is that the EZL was eventually overheating due to the extra resistance, and unable to provide enough juice when warm. Car runs great now!

 

[Duh_Vinci]

An update on modified rotors per @robm.UK instructions above:

About 10 weeks of various driving, short trips, long trips, sitting for as much as 5 days not driven - there is no more moisture related issues! Quite happy, and thank you again for the research and visuals Rob, appreciate it! One happy car with a happy driver!

Regards,
D

 

[robm.UK]

Thanks for the update. It’s good to hear that my fix is working out for you.

No need to go and buy a new set of caps just yet. Bosch and BERU will probably put their drop in sales down to Covid. But ssshhhhh.... we know better.

Another great intervention! We’re only a small island but we have the beating heart of a V8.

 

[JCM1]

Hi Rob,
I made your modification (first pic) in November 2020 and have had no problems at all here in Vancouver, BC where we have a wet humid environment. Previously, the caps/rotors would only last 3- 6 months as seen in the second pic.

All the best,

Joe

 

[gerryvz]

Nice to hear that @robm.UK's fix is working. I have an old set of caps (that I took off of my car last year, but were working fine) and I think I'm going to modify them, as well as two other sets of used caps that I have in my parts stash.

 

[Tanel]

A link to the full report on fixing the misfire problem on CIS-e engines can be downloaded HERE

It seems the full report-link is no longer functional.

Is there any chance someone has it saved to share? Thanks!

 

[gerryvz]

I think I have it somewhere and can post.

 

[Tanel]

I think I have it somewhere and can post.

That's billiant of you to offer - but no need to go through the trouble. I found the full report in another thread at BW. For anyone else looking it can be found here: Microsoft OneDrive

 

[gsxr]

Attached to this post as well for posterity.

 

[gerryvz]

Links to the doc in this thread have been pointed now to the @gsxr's post above, so that the doc is archived and will be able to be downloaded well into the future.