93 500SEL | No fire from right coil - PeachParts Mercedes-Benz Forum

ijohnellis · #1 11-03-2015, 05:09 PM

Background:

1993 500SEL // 200K miles // Excellent Condition

I purchased this car in June from the original owner. He purchased it from the local dealer and it was serviced at the dealer for the entire life of the car. It never missed a service until the 180K service, when he was getting rather old and didn't drive it much. It's now at 200K and will be getting those services soon.

Not long after I bought the car, the water pump began weeping. It took me a few weeks to get the time to replace it, and in the meantime I kept distilled water in the trunk and topped it off as necessary. A few weeks ago, I opened the expansion cap to top it off without realizing that the water level was higher than I anticipated, so water started spouting on the engine. After a few moments, I threw a towel over the expansion tank to prevent more water from dousing the engine. The car was not running when this happened and it was straight water at this point.

When I started the car to drive it later that day, it ran very rough and I assumed I'd gotten the cap or plugs wet. After several days of trying to dry everything and blowing everything off, it still would not drive normally.

Symptoms:

The engine is only firing on four cylinders. When I put the transmission in D, it stalls after just a moment. If I put the transmission in reverse or first, it will drive. When I manually shift from first to third, it will stall through second, but then shifts to third and then fourth without issue. I learned this by trying to drive it to dry the engine, initially.

Steps Taken to Cure:

I replaced the following items

Water Pump
Both caps and rotors (Beru)
Spark plugs (Bosch)
Right coil (Bosch)
Crank Position Sensor

I have read about 40 hours worth of posts everywhere using every search term conceivable and have yet to fully comprehend what could possibly have cause the issue and what the issue is. I have disconnected power to the injectors for the non-firing cylinders while troubleshooting.

I suspect the EZL/ICM, but no water even reached that side of the engine. Of course, I am assuming the water on the engine caused the issue, but that may be a false cause. This engine ran perfectly prior to water spilling onto the engine.

Any ideas or further insight? I do have an appointment in a couple days with a semi-retired Mercedes mechanic who came up with these cars. There is a wonderful local indy shop that I trust, but they're a few weeks out and this mechanic came highly recommended from another Mercedes owner.

Thanks for reading the essay I've written as my first post.

John

duxthe1 · #2 11-03-2015, 07:29 PM

If you've replaced the offending coil its down to the EZL.

ijohnellis · #3 11-03-2015, 07:34 PM

That's all there is left, right? What could the water on the passenger side of the engine have possibly done to cause the EZL to fail on that side? That's mostly a rhetorical question, unless there's a plausible answer.

duxthe1 · #4 11-03-2015, 07:35 PM

Likely unrelated. **** happens.

ijohnellis · #5 11-04-2015, 04:49 PM

Update:

The Cam Position Sensor was faulting with an open circuit. We disconnected the cable and the engine still started the same. New sensor will be in tomorrow and I'll hope that was the culprit. I would like to understand how the single cam sensor functions in a dual distributor system, if anyone has knowledge or a source.

duxthe1 · #6 11-04-2015, 10:14 PM

Cam sensor is just for synching injection, and will only delay starting if failed.

ijohnellis · #7 11-05-2015, 01:41 PM

So I installed the new camshaft position sensor and it didn't correct my main problem. Replacing that and reconnecting the injectors helped with smoothing out the shifting and overall driving experience, of course, since the whole sensing system was out of whack.

I'm left with the EZL as the remaining component. Honestly, WTF?

I wonder if the hot water that spilled out of the expansion tank and onto the vacuum line connected to the EZL caused a massive vacuum draw and damaged it.

I am irritated and would think that the EZL being bad would throw a code.

Ferdman · #8 11-07-2015, 06:27 AM

ijohnellis, from my experience if an EZL is bad the engine will not start.

ijohnellis · #9 11-07-2015, 12:33 PM

I have read that a lot, but then I've read where only one bank is shut down. I'm going to pull codes again to determine if I can draw anymore conclusions, but I'll be purchasing a new EZL. It either corrects the problem or provides me with a backup. I'm not seeing any other solution.

I do wonder exactly how the second gear stalling comes into play. It drives in every gear, except second. Obviously, this is a second-gear start, so it must relate to a fail safe, but I don't know. I've looked over some diagrams and the sensors used in the ignition system, but I haven't applied a lot of time to understanding them. It may not matter, but it's curious.

Ferdman · #10 11-08-2015, 06:57 AM

ijohnellis, the EZL that I purchased for our 1991 300CE cost over $1,200. Before spending that amount of money, for what could end up being a spare part, I recommend having your local MB dealer diagnose the problem.

ijohnellis · #11 11-17-2015, 02:26 PM

So many of these posts die without a final resolution, so I'm going to post mine now.

I ended up purchasing an EZL (Ignition Control Module) on Ebay for $129 (not my favorite idea, but it provided me with purchasing protection that a boneyard purchase would not).

I disconnected the negative battery terminal and applied Arctic Silver Thermal Paste and installed the new unit. After removing the old EZL, the thermal paste was still tacky. I simply cleaned it off the engine to install the new one. When I started the engine, it roared up with a moment of hesitation, but all 8 cylinders were firing!

I purchased a '71 220D for $500 last week, that I happened upon at a shop in the middle of nowhere, but I love them and it gave me something to drive while I fixed this issue. Needless to say, though I adore the old diesels, when I got in the 140 to hit the highway and work out the recent tuneup, I was ever so impressed! What a ride and so much power. It was like a new car. Hit 120MPH so easily that I'll likely lose my license in no time.

In summary, right side (passenger) cap and plugs got wet. Started the car with wet components and probably shorted the EZL for that bank. Replaced caps, rotors, plugs, camshaft position sensor, crank position sensor and right bank ignition coil. None of those corrected the problem, so I replaced the EZL (Bosch number 014 545 43 42 with Seimens number 013 545 64 32) and the problem was corrected. I tried to find some conclusive answers to whether the newest part numbers were ideal and why, but never really found anything to support spending more for the 015 545 61 32 part over the older version I ended up purchasing. Now that I know this corrected the problem, I may opt for one as a backup or would choose to spend the extra cash in hindsight, but with the new parts installed, it is far more powerful and responsive than before, so I don't know that the newest EZL matters at all. New ignition maps would be the only benefit, if they existed.

I didn't change the plug or ignition wires, as they were in good shape and are a nice Beru set. I also didn't replace the left bank ignition coil, but I will likely do that soon. It's just too damn cold now and it's a pain to access.

As for the thermal paste, I did a whole bunch of research and found that this paste (which I have used when building a computer) has one of the best heat transfer capacities in tests against ceramic/silicone-based pastes. Some of the ceramic/silicone pastes were also highly rated, but this one contains 99% silver, so I felt it would be the best solution for this application.

Hopefully this answers most or all of the questions someone might have regarding this problem. I couldn't find all the answers I was looking to understand, so I'm trying to include them all here.