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95 600sel m120 engine loss of power, strong smell and little smoke of unburnt fuel

21219 Views 115 Replies 10 Participants Last post by  will_c140, 
KnigolubS600L
Fellow members, i am in dire need of help!

Here is a puzzle for you, the car (95 w140 s600l/600sel its with the older m120 engine) is experiencing the following symptoms, the engine sort of gets (for a lack of better word) clogged/flooded, loss of power, it smells very strong of gasoline if you stand behind the car, not all cylinders are firing. The issue does not appear all of a sudden but sort of gradually within an hour of driving power is getting less and less, and when driving the fuel consumption gauge is constantly at max. It does not look like it burns oil or not much at least, and when the issue appears and the engine is revved for some time it sort of cleans itself (or maybe it passes on its own) with white/bluish smoke and runs fine until the next episode after a couple of months depending on driving.


When the car is started cold there is no smoke, and also when the engine is not "clogged" there is again no smoke and runs very nice.

This happened on one of the longer trips and has been re-occurring ever since with shorter intervals.

Some background on what was done on the car - new spark plugs, new distributor caps, new oxygen sensors, the dreaded harness for MAF sensors was rebuilt up to the computer box, harness for injectors was purchased new and original.

A compression test of the engine was performed and showed good compression on all cylinders, also when performing star diagnosis normal live readings from engine were found and no apparent error, however when we did the diagnosis the car was ok (its hard to get it to the shop in that condition for a diagnosis now).

Self troubleshooting was performed while the problem was present on the spark plug cables and an interesting thing was found, when we unplug cables from passenger side engine is sensibly affected, however when we do it from driver side its hard to tell if engine is affected at all, that turned our attention to the left coil, we had a spare new cable for the coil and we tried it but it did not show any improvement, we will try with a new coil (then again a failed coil will probably be failed permanently and not intermittently for the car to run ok for a while) and will also try with different ignition module (the square module that cables connect to on top of each fender). Throttle bodies have not been inspected but are humming as supposed to.

It sounds maybe like the spark is not strong enough for the fuel to get burnt or that fuel management is not ok.

Have not inspected the catalytic converters yet as i dont really understand how to inspect them and if they can cause such havoc.

So many things have been addressed on this car, can someone shed some light or come with wit a brilliant logical idea as to what might be the problem its so frustrating to see my well preserved baby struggle like this! I fear to think if its something inside the engine yet i am hopeful since the symptoms are not constant (indicative of a ware of inside components) and are coming and going.

Fellow V12 owners and mechanics and members, can we solve this?
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KnigolubS600L
3
Steve_B said:
The variable camshaft timing is meant to

Losing power, shaking, smoke -- to me, it seems like the combined effect of several faults. Being intermittent, I think the root cause is an electrical gremlin of some sort.

Steve
Click to expand...
Hi guys a summary of what happened today. We did a STAR Diagnosis, checked everything and here are the results:

Car is still working bad which was nice for the stardiagnosis, stopping the injectors on each cylinder (from the software) revealed that cylinders 8,9 and 12 do not affect the work of the engine at all, meaning injectors are not squirting or are squirting all the time? Live readings of the engine however revealed injector squirt time to be 4 ms as expected but that is not squirt quantity right? I hope that these three not working cylinders are the problem so that we have a direction.

Interesting thing is that we replaced two spark plug cables on cyl 8 and 9 and spark plug only on cyl 8 (we did not touch cyl 12 as it harder to get to), hoping that engine will start working better, however there was no difference. Yet we did measure resistance in the harness and its obvious that there is electricity going to the injectors.

Our next planned step is to try with my friend's distribution cap and rottor, since we checked almost everything on the whole chain! And if that does not yield results i guess next suspect are the injectors? I doubt clogged catalitic converters, can cause only those 3 cylinders to stop working?

There werent any other apparent errors other than, an error on LH2 module but (my friend can confirm) it was something temporary because we switched the modules the day before and we also unplugged the injectors. I think it dissapeared afer being cleared.

Also when we started the car the MAF sensor reading fluctuated alot but only for a few seconds and then stayed steady (i hope its normal behaviour since we did change the wiring).


Not sure but when we looked way inside the cylinder after the sparkplug was removed i saw it was dirty (oil or whatever) is that how its supposed to be?

Looking forward to your reflections on the results.

Some photos of the spark plug and inside the cyl (not very clear though):




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shotgun600
*We measured the voltage of the fuel injectors and there are 12v when the car is on contact and around 13.5 when working on idle.

So there are 2 possibilities:
1.Those 3 injectors are faulty.

2.The cap and rotor are faulty somehow.
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KnigolubS600L
3
correction on my previous post, we measured the voltage to the injectors.

trying to repost the pics again how does it look to you?




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arklatexV12
Okay, following that....

1. Your problem is not camshaft adjuster magnets.

2. No spark to cylinders 8, 9, and 12 is what I'm understanding from that. Check caps & rotors again.

3. If that doesn't work try a cam sensor. Just try it.
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shotgun600
Will do it.

*And there is a third scenario (worst)
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KnigolubS600L
2
Hi everyone,

a followup update on what we did today.

Replaced caps and rotors on driver side and cleaned the spark plugs in cyl 8 and 9 (12 is hard to reach).

The car started to run a little better (looks like more cylinders were firing), but we dont have diagnosis to know which for sure. But i personally think it was from cleaning the spark plugs rather than replacing the caps, as the car was still not working on all cylinders.

Ok so the problem looks to be that something is getting on the spark plugs (when you smell tem it does smell of gasoline but it can also be something else), so can someone confirm if it can be from not properly working injectors (we are going to remove, inspect, test and clean those next any tips??), or is it something inside the engine, like worn out valve seals? The thing is if it was getting oil on the plugs i thought it would smoke alot of oil, it does smoke alot now but it looks to be gasoline and it smells of it.

Or it might be that its leaking veery little oil, just enough for it to get on the sparkplug, as the issue appears after driving for some time. But again, there is the mystery of not smoking oil from the exhaust, it all of a sudden clogs and starts to loose power.

Any suggestions are appreciated, here is a photo of a sparkplug from a working cylinder that did not experience issues (i think). How does it look to you?


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S
.

Ok so the problem looks to be that something is getting on the spark plugs (when you smell tem it does smell of gasoline but it can also be something else), so can someone confirm if it can be from not properly working injectors (we are going to remove, inspect, test and clean those next any tips??), or is it something inside the engine, like worn out valve seals? The thing is if it was getting oil on the plugs i thought it would smoke alot of oil, it does smoke alot now but it looks to be gasoline and it smells of it.
Click to expand...
This is my post #1000 on BW, so I hope it is a good one.

1. You never answered my question -- when was the rotor from the picture installed on your car? The gap between the cap terminals and the rotor seem huge.

2. Your pictures seem to show plugs that are wet from raw fuel, which points at ignition-related issues.

3. Of course, spark and fuel delivery are intertwined and proper spark will NOT do much if the fueling is out of wack.

Expanding on this -- you mentioned faulty injector. This can happen, on cars that see low quality gas, are not driven regularly and not driven "hard" on time to time.

Let's say one injector is stuck closed, for the sake of argument #9 (you can confirm that the injectors click by listening with a stethoscope or a long screwdriver) or more likely, does not flow properly. The same will apply to #8 and #12, but I am just giving you an example with #9.

When an injector has low flow rate (or any significant deviation out of spec), in closed-loop, that banks' O2 sensor will send a voltage signal to the fueling ECU to get rid of excess air in that bank exhaust stream, and will richen all injectors on that bank until the excess O2 is eliminated. In most cases, #9 will then fuel correctly, but the other five injectors on that bank will flow rich.

Having said all that, I think you need to go back to the basics. Confirm compression on all cylinders, confirm all spark plugs and HT leads.
confirm the PROPER FIT of that questionable rotor, and clean/inspect all spark plugs. They are NGK -- a reputable brand -- but the gurus here seem to favor BOSCH F8DC4 (yes, the Russian-sourced ones that come in shiny MB-boxes)

Good luck,
Steve
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shotgun600
The cap and rotor are on that car since my friend bought it 2014-2015. I don't know for sure, but they are not from yesterday on that car.

Yes, the gap between the cap terminals and the rotor seems huge, I thought it too. But today I removed my cap and rotor (which are from the other type, not like his) and the gap seems the same.

The car worked a little bit finer, but that's because we cleaned cyl 8 and 9 sparks, not because we mounted my cap and rotor on his car....

So, the next step is to remove the fuel rail (any help, tips and tricks, is welcome) and take injector 8,9 and 12 to cleaning with ultrasound.

If that does not resolve the problem, we will have to take the car to a car service. The problem is that in our country you can't trust anyone, especially car mechanics and service owners.

Service owners will often lie you about the problem to take more money, car mechanics will make bigger mess with the car....
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V
Hi there, I shall introduce myself properly in due course, pending the imminent arrival of my first W140.

Reading this thread through I have a couple of questions which might help solve the non ignition problem:

1. Were the plug wells/HT boots oily? Pictures not clear on my tablet.
2. Has the car had the camcover gaskets, including the plug well seals, replaced?
3. When were the plugs last changed?

Even the 'good' plug looks oily... just not bad enough to prevent a clean spark. Yet.

Does these automatically up the injector opening times for cold starts? I am wondering whether cold start enrichment might be washing the electrodes clean, but as the injector opening times drop back as engine temp increases, it's allow just enough oil onto the plugs to foul them...
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arklatexV12
The injectors have a range of +/-25% to work with (called fuel trim) in regards to corrections off of baseline. Plus I doubt multiple faulty injectors would all become symptomatic at once. Your issue is assuredly spark, I just can't figure out what at this point. Go with Steve's opinion and throw new plugs at it. People have run into issues using anything but the Boschs, though I believe that to be a tall tale, who knows?
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S
If that does not resolve the problem, we will have to take the car to a car service. The problem is that in our country you can't trust anyone, especially car mechanics and service owners.

Service owners will often lie you about the problem to take more money, car mechanics will make bigger mess with the car....
Click to expand...

I am sorry to tell you that in the US too, everywhere you show up with an old MB (or other *fancy* car) you should expect to be taken advantage of. God knows how many perfectly good cars ended at the crusher because of greedy mechanics....

Sounds familiar..?

http://www.benzworld.org/forums/off-topic/2831362-we-all-eastern-european.html

Steve
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S
6
The cap and rotor are on that car since my friend bought it 2014-2015. I don't know for sure, but they are not from yesterday on that car.
Click to expand...
I will say it again. New part doesn't necessarily mean a good part, especially if they are aftermarket and with unknown origins (the Made in Italy stamp means nothing in today's world).

This rotor doesn't look like it has seen lots of use. Look at the distributor cap and rotor I removed from my car (they are the ones that the engine had when it left the assembly line 24+ years ago).

The diameter of the cap (distance from post to post is 90 mm).
The rotor measures a hairline smaller than 45 mm, which means that the cap post and the rotor should almost "kiss" when the spark is being transmitted.

I know that the parts will be expensive, but at this point, I am almost convinced that you've got to start with a KNOWN GOOD cap/rotor and NEW spark plugs on the bank that is giving you problems. Cyl. #12 too, no excuse (it is tight in the back, but doable).

Verifying the resistance of ALL HT leads on this bank is also a must (unfortunately the replacement set is over $300 and will require pulling the intakes)

Yes, the gap between the cap terminals and the rotor seems huge, I thought it too. But today I removed my cap and rotor (which are from the other type, not like his) and the gap seems the same.
Click to expand...
The picture could be misleading, but this gap is over 1 mm. That's TOO MUCH!
The spark plugs are gaped about about that.

Yours:


Mine:



Good luck,
Steve

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S
And I forgot earlier -- new ignition coil.

I would do two, but this could be tough to swallow -- for me $80 a piece is something I can live with, while for you, that could be the weekly family budget.

Please see here -- this thread has been running for some time. A V8 car, not V12, but the idea is similar. If the coils are 20+ years old, and if there has been an ignition fault of some kind....:

http://www.benzworld.org/forums/w140-s-class/2744882-s500-engine-misfire-when-warm.html#post16076426


Steve
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shotgun600
My cap and rotor are exactly like yours, and they are original Bosch, not made in Italy like his. Nothing happened when we mounted them on his car.

Also, may be pictures are misleading, the gap between my rotor and cap is the same, and my car runs very well.

We tried another set of high voltage cables on the problematic side - nothing happened.

We tried almost everything....

We decided to buy a compression tester and do a compression check. If the compression is OK, we will buy other spark plugs - that Bosch that you mentioned "but the gurus here seem to favor BOSCH F8DC4".

For me the reason for that problem with 8,9,12 cyl is one of those last possibilities - no compression or fake sparks (not real NGK but some Turkish shit).
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shotgun600
Steve_B said:
And I forgot earlier -- new ignition coil.

I would do two, but this could be tough to swallow -- for me $80 a piece is something I can live with, while for you, that could be the weekly family budget.

Please see here -- this thread has been running for some time. A V8 car, not V12, but the idea is similar. If the coils are 20+ years old, and if there has been an ignition fault of some kind....:

http://www.benzworld.org/forums/w140-s-class/2744882-s500-engine-misfire-when-warm.html#post16076426


Steve
Click to expand...
We tried my ignition coil....nothing happened.
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S
For me the reason for that problem with 8,9,12 cyl is one of those last possibilities - no compression or fake sparks (not real NGK but some Turkish shit).
Click to expand...
This is probably the reason NOTHING HAPPENED when various parts were swapped -- the plugs are not able to produce proper spark anymore.

I will be surprised if there is no compression, but who knows -- your friend is probably owner number XY and the history of the car is very likely unknown.

Steve

PS Check the leads too. Resistance should vary with the length, but the numbers should be x2 or x3 different, at most. x10 or higher will be suspicious.
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Merc-S600
2
KnigolubS600L said:
Hi all,

here is a clip from today showing how it shakes on idle clearly not working well the issue is still present, strong fuel smell, will continue with troubleshooting after star diagn.

https://www.youtube.com/watch?v=nXviZPnQ6PI

Just wondering if it is something like crank/camshaft related (sensors, magnets) after reading arklatexV12's thread, it probably wont appear on the star diagn? also what to look for specifically on the star diagnosis apart from codes, maybe live readings?
Click to expand...
I just watched this video of yours ,wasn't able to see it before ,all black no screen .

See my codes in post # 13 & 14 . Mine has the EGR removed that's why the code .
http://www.benzworld.org/forums/w14...-camshaft-sensor-location-2.html#post12625129

The hood shaking was exactly what mine did ,it drove me nuts ,Refer to the link below , my shaking hood Vid on Pge 2 ,the fix Post# 28 & on .
http://www.benzworld.org/forums/w140-s-class/2405041-mercedes-ezl-ignition-control-module-air.html .
Maybe this applies to you as well .
Change Spark Plugs at the Firewall as well #12 , you can either remove that wiring tray by lifting it of the clips or squeeze an extension for sparkplug socket behind the tray into it ,you end up directly over the plug , one socket extension one plug socket , insert a small rubber like cut out Garden hose into the socket (unless it has it) to lift the plug out & re-install it (ad a little oil around the plugs socket Thread so it comes of easy when re-installing) otherwise the socket will stay behind & you be going fishing for it then , you must change all Plugs not just 10 or 11.:thumbsup:

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KnigolubS600L
5
Hi guys, first of all thanks for all the icomming comments so far its great. We took a couple of days off enjoying the sun, before decending.back in to the beast's den and working on it :grin

Here is an interesting update from today's events.

We cleaned the spark plugs on the non working cylinders and changed the cables. The car started to work perfectly, i thought to myself that this is just avoiding the root cause (whatever is clogging the spark plugs), until we deided to check the resistance on the spark plug cables. The results were pretty bad 2.4-2.8 kΩ. My friend's cables resistance is at around 1-1.3 kΩ (if i remember correctly which is according to specification). It looks like at some point all the spark plug cables were replaced with something that does not even look original, even the one leading to the coils. Photos to follow (if you can please compare on yours?).

Now we were aware that the cables were not proper, before changing a ton of parts but we did not measure the resistance up until now.
To be honest we decided against the compression test because alot of prepping is needed and it very much sounds like we found the root cause (fingers crossed).

Our action plan is to change the spark plug cables and possibly spark plugs (for now not sure if we will remove the intake manifold to do it properly, but rather connect them and drive as such).

If however the problem returns after replacement of cables and possibly spark plugs (hopefully it wont), we will have to go back to the injectors and do the compression test.

So its very possible that you were right in saying its an electical gremlin of some sort.

Here are photos ot the plugs of the cables please compare with yours and let me know:

bad cable resistance




good cable resistance


strange not factory plug please compare


Resistance specs
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S
We cleaned the spark plugs on the non working cylinders and changed the cables. The car started to work perfectly, i thought to myself that this is just avoiding the root cause (whatever is clogging the spark plugs), until we deided to check the resistance on the spark plug cables. The results were pretty bad 2.4-2.8 kΩ. My friend's cables resistance is at around 1-1.3 kΩ (if i remember correctly which is according to specification). It looks like at some point all the spark plug cables were replaced with something that does not even look original, even the one leading to the coils. Photos to follow (if you can please compare on yours?).
Click to expand...
Well, this seems to be a step in the right direction. Creative work by someone else always comes and haunts.
This is why I asked repeatedly if this car ever ran well with that rotor arm (compare with mine, the brass electrode should be completely covered with insulting material and yours is partially exposed).

I will measure my HT leads, but offhand, 2 kiloOhm is not too bad. Many aftermarket manufactures do that for the older distributor-based ignition systems to suppress RFI (radio frequency interference).

BUT, please do make sure the spark plugs you are using are of the NON-RESISTOR type. Again, F8DC4 is what the long-time MB owners here swear by.

R-type plug, on top of some "restriction" from coil to plug due to leads and cap/rotor may prove too much -- weakening of high voltage needed for a proper arc could be the reason the engine is not running well.

Steve

PS I have to ask -- is bank 1 also fit with the aftermarket HT leads that you have on bank 2? Have you measured resistance there? Whatever you do, don't change plugs/leads on one side of the engine...
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shotgun600
On the passenger's side the cables are the same - 2.5kOhm resistance end to end. Those cables don't even look like aftermarket ones because of the connectors to the caps - they are different from my original ignition cables and from my aftermarket ones.
We didn't make pictures but we will and will post them.

Also the connectors of the cables between the coils and the caps are not like my original ones and my aftermarket ones. Originally connectors to the coils are different than those to the caps, but in his case both ends of the cables are the same...

Can't explain it good so I will show picture soon.

For me the problem is generated by the ignition cable. KnigolubS600L will buy a new aftermarket set from E-bay.

The problem is that we are not sure that we could take off the intake manifold without fucking up something else....

*As you see AllData tells that they should be 1kOhm +-20% end to end.
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