Ignition problem

[J. M. van Swaay]

1994 E500, 124K miles

Engine running on 4 of 8 cylinders. Permanent condition, not intermittent. Pulled drivers side coil wire, no change. Reconnected drivers side coil wire and pulled passenger side coil wire, engine would not start. Concluded no spark delivered to drivers side rotor. Removed drivers side cap rotor and insulator, no visible damage, carbon traces, or moisture. Tried new ignition coil on drivers side, no fix. I have two known good EZLs, tried but no fix. (Yea, I know, hope I didn’t fry three EZLs due to bad coil, wire, etc..... Just seems very unlikely). Now thinking it could be the coil to rotor wire—would like to replace it and see what happens. All ignition components have been replaced during my ownership so would prefer to start with just the coil to rotor wire. Anybody know of a source for just this wire? All I can find are the complete sets...

Anything else I should try or consider?

Thought about pulling the passenger side coil to rotor wire and trying it on the drivers side to see if engine will start. As I recall, removing this wire will require removing pretty much all of the ignition and plug wires. Then if it works, I still need the replacement wire for the drivers side...

 

[Glen]

I’d try swapping the rotors side to side to see if the no spark condition follows. Then the caps if not before changing the coil wire.

 

[gsxr]

Are you certain you swapped the correct coil? Driver side distributor should be the coil closest to the fender, IIRC.

Your idea to borrow the passenger-side coil wire will work as a test, but is a nuisance, as you describe.

I agree with Glen, first try swapping the cap/rotor/insulator from side to side and see what happens.

Very, very unlikely to be the EZL if known-good ones didn't make a difference.

If it is a defective wire, I'd be suspicious about the condition of the rest of the wires, and replacing the entire set might make sense (along with TWO new ignition coils, while you're in there). Are the wires original/factory? If not, what brand/type are they?

 

[gerryvz]

Driver side distributor should be the coil closest to the fender, IIRC.

The driver's side distributor coil is the one that is closest to the engine. The passenger's side distributor coil is the one immediately next to the series resistor, and the fender-wall.

As far as I know, @gsxr, your own photos show the "long" coil wire coming from the coil nearest the fender, and going across on the "X" tray to the passenger-side distributor cap. And the inner-most coil, the shorter wire to the driver's side distributor cap.

@gsxr is correct -- driver's side distributor is connected to the coil closest to the fender. I just went out to my car and double-checked it. False alarm.

Is the gsxr photo below, inaccurate?

 

[J. M. van Swaay]

On my car, the drivers side coil is closest to the fender furthest away from the engine, I’m certain because the wire from it goes to the drivers side cap. The wire set is Bosch, installed probably 30k miles ago along with new caps coils and rotors. I’ll try swapping rotor and cap and report back.

 

[gerryvz]

On my car, the drivers side coil is closest to the fender furthest away from the engine, I’m certain because the wire from it goes to the drivers side cap. The wire set is Bosch, installed probably 30k miles ago along with new caps coils and rotors. I’ll try swapping rotor and cap and report back.

You and the @gsxr are correct, and I edited my post above after double-checking on my car.

A couple of questions:

1) Are the four cylinders that are not running, one contiguous bank of cylinders (one side of the engine), or are they intermixed on both sides from one distributor cap?

2) Are you sure that it is four cylinders, instead of one, or two, or another number, that are not running?

My other question is whether a plug wire or and coil-wire have been mis-installed, meaning that you have a mis-fire rough-running condition rather than a non-firing four-cylinders issue.

Only three things are going to control or supply spark to four cylinders (whether contiguous, or on both banks) SIMULTANEOUSLY:

a) the EZL
b) one of the coil wires
c) one of the coils

The distributor cap and rotor supply spark on a sequential, not simultaneous, basis, though they could also be considered.

If you had a bad EZL, you would have four cylinders on one bank not running, I believe. It is fairly rare to have an EZL fail in the mode where four cylinders don't run (though it happened to me) -- I'd say 80% of the time the EZL completely fails.

If you had a bad coil wire, or a bad coil, then you would have two cylinders in each bank that are not getting spark, at the same time.

My guess is that it is a bad wire, or a bad coil. More likely a wire.

I would as said remove the caps and rotors, and inspect them carefully for any physical damage. The caps of course at their contacts. Then swap them part by part as @Glen said, to test.

 

[gsxr]

Is the gsxr photo below, inaccurate?
View attachment 112750

No, the photo is accurate... but does not clearly show the wire routing. The driver side coil wire loops up and back towards the engine, out of the frame of the photo. But the coil closest to the fender does connect to the driver side distributor cap.

Note that both the distributor cap and rotor each have resistors built in to each terminal. It's extremely unlikely that all 4 would fail simultaneously on the cap, but if the rotor is "open" (infinite resistance), that would cause all four cylinders to not fire. I'm thinking coil wire, coil (already tested, but double check), or wire.

 

[J. M. van Swaay]

Yea, lots of thoughts I’ve had as well..... I don’t know if one coil feeds one side or if one coil feeds 2 on one side and 2 on the other. When I first tried diagnosing this problem, I felt the exhaust manifolds (heat) on both sides after a short run of a minute or two. Both sides felt the same.... Makes me think one coil feeds 2 left and 2 right.... I suppose I could figure it out by tracing the plug wires from one cap.... Because there was no difference in run condition when disconnecting the drivers side coil, I’m pretty sure it’s 4 of 8 cylinders not firing.... I’m gonna think about this for another day or two..... I’m hoping for an aha moment....

 

[gsxr]

JM, you are correct, each coil/distributor fires 2 cylinders on each bank. This allows the engine to run (and, the car will drive, don't ask how I know) with one coil or distributor completely failed.

You definitely have 1 side not working as proven by your test which resulted in a no-start condition. I'm still thinking bad rotor or wire.

 

[J. M. van Swaay]

So far, I’m thinking most likely rotor or coil wire. Pretty sure nothing is incorrectly installed because condition presented itself after many miles of trouble free running. (In other words, I didn’t have my hands in the pie just prior, but I certainly am very capable of bonehead mistakes...)

 

[nocfn]

Did you measure resistance on the coil wire(s)?

 

[J. M. van Swaay]

No, I did not measure any resistance values. I’m a shade tree mechanic at best, but it has been my experience that ignition related electrical problems do not lend themselves well to traditional diagnosis. Something that “measures up fine” on the bench may have an entirely different characteristic when hot or under load.... That being said, I’m pretty handy with an ohm meter, if I were to ”check” a coil to rotor wire, how would I do that and what would I be looking for?

 

[gsxr]

The coil wires should be near zero ohms. Or at least low single digits, like 1-2 ohms, accounting for resistance of the test leads and meter error. A bad wire would be open (infinite, or millions of ohms).

 

[nbvcxw8000]

I had this problem with one rotor completely failed. When I measured it with ohmmeter (low voltage), it was good (1k Ohm), but yet it was dead with high voltage!

 

[gsxr]

I had this problem with one rotor completely failed. When I measured it with ohmmeter (low voltage), it was good (1k Ohm), but yet it was dead with high voltage!

...and that is why troubleshooting high-voltage ignition parts is difficult! They can bench test OK but fail in use. VERY frustrating. Even worse if you get a new part that is defective out of the box (thankfully, that is not common).

 

[195910]

...and that is why troubleshooting high-voltage ignition parts is difficult! They can bench test OK but fail in use. VERY frustrating. Even worse if you get a new part that is defective out of the box (thankfully, that is not common).

More common now Dave

 

[J. M. van Swaay]

Update:

Took a chance and replaced the rotor with a new one. For a brief moment, I thought I got lucky because the car started and idled normally. However, after a short drive, it became obvious that 4 of 8 cylinders were periodically dropping out. In other words, engine cycled between running on 4 and running on 8. I’m pretty sure this means rotor/cap/insulator problems. Think I’ll try a new cap next unless someone else has a better suggestion.

Stay tuned....

 

[195910]

Are you able to check which set of cylinders are dropping out (Scope,HHT) ? if so, swap the caps and rotors to the other side and see if the other set of cylinders starts to drop.

 

[gerryvz]

That’s what I asked — are the cylinders that are dropping out all on one bank, or in both banks.

The car really needs to be put on an oscilloscope so as to see what’s happening with all cylinders at the same time, electrically.

This will allow the diagnosis to be narrowed down quite quickly.

 

[nbvcxw8000]

By removing the spark plugs, it should be possible to see the four cylinders where there is no ignition (according to different color of spark plugs).

 

[J. M. van Swaay]

First, thanks for all the input. I’m sure the best E500 minds in the country are on this board. We E500 owners are lucky to have this resource!

Better diagnosis via HHT or scope would be the most prudent course of action. Unfortunately, that’s not available to me here in the Florida Keys. If someone knows a good shop in Miami that might be a possibility, but I would have to have the car towed there and it’s 60 miles away...

I’m pretty sure the cylinders that are dropping out are those that are feed by the drivers side cap/rotor/coil. In my mind, I confirmed this when there was no change in the run condition when this coil wire was disconnected. Also, when I reconnected the drivers side and disconnected the passenger side, the car would not start at all. The fact that I had improvement (intermittent normal run condition) after replacing the drivers side rotor leads me to believe that the fault lies in the drivers side ignition system. I had not considered that I might be able to determine which cylinders are not firing by reading the spark plugs, but I’m not sure how that helps me.

Once again, I’m in a ”diagnosis by part replacement“ mode. A process that a competent mechanic would never engage in. In this case though, it’s probably my best option. The parts are not crazy expensive, and the labor to swap them out is minimal. Also. given the the history of ignition related problems that have been solved by cap/rotor/insulator replacements. I think I’ll continue the process.

To quote Johnny Cash, “I’ll get it one piece at a time”. Only problem is I can’t bring the parts home in my lunchbox... And it will cost me more than a dime...

 

[gsxr]

JM, I agree with your diagnosis. It appears to be the driver side components which are at fault. Since you swapped the rotor already and had a temporary cure, that is promising. Just curious, what brand new rotor did you install?

 

[J. M. van Swaay]

It was a Bosch rotor.

 

[J. M. van Swaay]

Installed new Bosch cap, problem fixed!

 

[gsxr]

Congrats! How old (years & miles) were the bad ones?

 

[sheward]

Did you see anything noteworthy that would explain the problem such as arcing etc?

drew

 

[gsxr]

FWIW... I've seen parts that looked perfect run terrible, and parts that look terrible run perfect. Neither scenario makes any sense.

It is really, really difficult to diagnose high-voltage ignition stuff visually (except when looking for arcing at night from bad wires!)

 

[sheward]

+1. After reading so much about this issue I'm trying to gather confirmation that perfectly good looking parts can indeed be bad. I've actually had very little trouble with this issue over the years.

drew

 

[LWB250]

Considering that the OP is on Key West is a giveaway for major humidity/salt air issues. I had a W140 that was parked within 100' of Tampa Bay for 4 days at a stretch and it always ran like garbage for the first few minutes until things warmed up and the condensation burned off.

Dan

 

[gsxr]

Considering that the OP is on Key West is a giveaway for major humidity/salt air issues. I had a W140 that was parked within 100' of Tampa Bay for 4 days at a stretch and it always ran like garbage for the first few minutes until things warmed up and the condensation burned off.

Dan

Dan, you know these cars couldn't have been like that when brand new back in the 90's. I'd still like to know what the root cause is for scenarios like you describe above. MB would have been flooded with warranty claims for every M119 parked near water in the 90s'...

 

[LWB250]

Dan, you know these cars couldn't have been like that when brand new back in the 90's. I'd still like to know what the root cause is for scenarios like you describe above. MB would have been flooded with warranty claims for every M119 parked near water in the 90s'...

Agreed. I would be interested to know as well.

Dan

 

[J. M. van Swaay]

Just looked at my maintenance records, all ignition parts (caps, rotors, wires, coils) were replaced about 10 years / 40K miles ago... A little older and a few more miles than I thought....

 

[J. M. van Swaay]

By the way, there were no visible defects in the cap. No carbon traces, no cracks, nothing. Looked brand new....

 

[a777fan]

Gah! The ignition demon strikes again!

Glad you got yours sorted. Hope it returns many many happy miles now.

 

[J. M. van Swaay]

Problem is back. Same run condition, starts and idles poorly (probably on 4 of 8). Same start and poor idle with drivers side coil to cap wire disconnected. As before, with drivers side coil to cap reconnected and pass side coil to cap wire disconnected, car won’t start at all.

Since initial post caps, rotors and insulators replaced with new (both side), drivers side coil replaced with new.

Also checked fuel pressure, readings around 3.5 bar, believe this is normal. Next step is to replace drivers side coil to plug wire. If that fixes it, I’ll replace the entire wire set. In the meantime, anybody know if I can get just the drivers side coil to cap wire? Anybody have a used wire they are willing to sell just to test?

Thanks!
J. M. van Swaay

 

[J. M. van Swaay]

I was able to find an MB part number for just the drivers side coil to cap wire:

115-159-08-18​

but I think it’s no longer available...

 

[gsxr]

J.M., part # 115-159-08-18 is bulk wire, sold by the meter... requires the threaded end fittings and rubber boots, plus a special crimp tool ($$$), to make your own. Not worth the effort. You cannot buy individual wires.

Based on your description, if the problem is intermittent, I also would suspect the wire(s). If the problem is persistent/permanent, the EZL is another possibility.

Do you know if your existing wires are original from 1994? Or have they been replaced in the past with aftermarket?

The complete Beru wire set is still available from PartsGeek for $205 plus tax, details below... note that they claim to have only ONE set left:

FYI - Beru spark plug wire set ZEF-635 | M119 Engine

Hi guys, I had been chasing a misfire on my 93' 500E for a month. I had replaced spark plugs, caps, rotors, and insulators behind the rotors thinking it might have been moisture build up behind the cap. Car ran fine cold, BUT would misfire as soon as it reached operating temperature. Then, I...

www.500eboard.co

W0133-1599712 | Partsgeek.com

Discount auto parts and accessories catalog for all foreign and import cars and trucks. Low Prices, Quality, Service and Free shipping.

www.partsgeek.com

 

[J. M. van Swaay]

Just ordered the Beru wire set, we’ll see what happens....

 

[J. M. van Swaay]

I had replaced the originals with a Bosch set about 10 years/40k miles ago...

 

[J. M. van Swaay]

Update..... you’re gonna love this...

Ignition wire set came yesterday, swapped out coil to cap wire on drivers side, no fix. (Kinda what I expected truth be told). Same condition as before, engine runs on 4 cylinders when drivers side coil to cap wire disconnected. When drivers side coil to cap wire reconnected and passenger side coil to cap wire disconnected engine won’t run at all. This confirms problem is in drivers side coil, wire, rotor or cap. Keep in mind ALL drivers side components replaced with brand new but yet problem still exists. As a last ditch desperate attempt, I swapped drivers side cap and rotor with passenger side cap and rotor. Yea, you guessed it, problem followed the parts swap, now she runs on 4 with passenger side disconnected and not at all with passenger side reconnected and drivers side disconnected. One more swap of the caps only confirms bad rotor now on passenger side.

Some lessons learned: I should have done this parts swap as both Glen and Dave suggested way early in this thread! I did suspect cap/rotor issues, but when replacing with new didn’t fix I was at a loss.... I simply wasn’t willing to consider the fact that a new (Bosch) rotor would be bad out of the box.

Ordered new Beru rotors today.... not ready to claim complete victory yet, but check back in a week or so...

 

[dreaming.haze]

@J. M. van Swaay - Solid update! Random, but I had the same issue earlier this year where I had replaced both rotors / caps / dust shields and rough running persisted. Narrowed things down in the same fashion of swapping caps/rotors across banks and the issue followed. Was a bad Bosch rotor out of the box from an FCPEuro order. Will be returning the failed part to them and making note it is a failed-out-of-box unit.

 

[gsxr]

Glad you solved the mystery, J.M.! But it's sad that you had a new Bosch rotor defective out of the box. I had a defective Bosch cap out of the box years ago, which drove me crazy troubleshooting.

Just a warning though, the Beru rotors from most vendors are now reboxed Facet (off-brand stuff). Not top quality, but may work ok. They are orange color.

The older Beru rotors were reboxed OE/Genuine Doduco, these are black and have the MB Star logo & part number. There were still a few available at some NAPA stores.

Buying from FCP with lifetime warranty might be worth considering for M119 ignition components...

 

[195910]

Check the dust shield (again) just to make sure its clean.

 

[J. M. van Swaay]

Just a warning though, the Beru rotors from most vendors are now reboxed Facet (off-brand stuff). Not top quality, but may work ok. They are orange color.

So which rotors are now recommended? I checked Autohauz, Rock Auto, PartsGeek, FCP and SM. Some showed the picture of an orange Beru, others had a picture of a black Beru... Still others contained “Karlyn/Bremi” in the description. It was somewhat difficult to know just what manufacturer you might get.... Ordered the Beru from FCPEuro based on previous recommendations....

 

[gsxr]

So which rotors are now recommended?

Foolproof source is OE/Genuine Mercedes from your favorite dealer. They were ~$80/ea from discount dealers last I checked. It was a lot nicer when you could get the same thing in a Beru box for half the price, a year ago.

I checked Autohauz, Rock Auto, PartsGeek, FCP and SM. Some showed the picture of an orange Beru, others had a picture of a black Beru... Still others contained “Karlyn/Bremi” in the description. It was somewhat difficult to know just what manufacturer you might get....

When a supplier changes what's in the box, it's not uncommon for vendors to either be very late updating their photos, or never update them. I contacted FCP in March 2021 and asked them to fix the COO and photos, and they did so. Previously they were still showing OE/Germany, after the update they showed orange/Italy. Anywhere else, it's sort of a crapshoot.

Bremi doesn't have a good reputation. After OE/Doduco, my second choice is Bosch, which as you found out is still not ideal. Side note - don't buy Bosch parts from Rock Auto, they are not an authorized dealer of Bosch, and apparently had some counterfeit products (M119 caps) in their inventory. Bosch's response was "don't buy from them".

Ordered the Beru from FCPEuro based on previous recommendations....

Beru had been the recommended source for years, since they were reboxed OE/Doducu. This changed late in 2020, details at the link below - sorry you didn't catch this update!

Beru rotors now made in ITALY, no longer reboxed OE | M119 Engine

YEP just got a pair today from FCP. BROWN PLASTIC like the Bosh distributor shields and stamped made in ITALY not GERMANY now!

www.500eboard.co

 

[J. M. van Swaay]

Dave, as always, thanks for sharing your knowledge! I have already ordered the Beru from FCP, guess I’ll wait and see what I get... Here’s a screenshot of the online listing...

 

[J. M. van Swaay]

Was looking back in my records, the bad Bosch rotor came from Rock Auto—maybe it was a counterfeit part?

 

[gsxr]

Was looking back in my records, the bad Bosch rotor came from Rock Auto—maybe it was a counterfeit part?

UGH. It is possible... but I don't know how to tell for certain. The distributor caps another forum member purchased from Rock Auto looked "wrong", as in sloppy manufacturing, compared to other Bosch caps. How many miles was the rotor in use before it failed?

 

[J. M. van Swaay]

I’ll have to look but I’m guessing only a few thousand miles. During that same time period I was experiencing intermittent run problems that were probably caused by the bad rotor. All the time I assumed the run problems were caused by the other cap/rotor, moisture, or some other issue other than the new rotor on the drivers side... Over the period of several weeks I replaced lots of parts and disassembled/reassembled the caps and dust shields several times looking for moisture or some other cause of intermittent loss of 4 cylinders... My new rotors will be here Wednesday, I’m cautiously optimistic.

 

[J. M. van Swaay]

Installed new Beru (the made in Italy orange color one with EVL 1831 stamped on the side) rotor. Have now completed 7 drive cycles with no misfires.... Think I’ll claim victory