THIRD (3rd) 300-24 EZL failure in 1 year

[ray_hennig]

Only other place I can think of where harmfull ARC RF might be generated on startup would be the the main pre-engaged starter solenoid contacts if they were badly worn/burnt. THIS would mean removing the SM and part stripping it to examine/clean said contacts. Unfortunately IIRC starter motor removal in the M104 NEEDS A SPECIAL LONG SOCKET.
Pre-engaged Starter Motor (Automobile)

An interesting thought.

The starter motor is not the original. It was replaced by a local garage about 8 years ago. I don't think they installed a cheapo one but it definitely wasn't MB original replacement.

I am inclined not to use the car until the new alternator is installed - I want to avoid another 1200€ going to MB Bochum.

Once installed, I shall run the engine and measure AC and other DC voltages in the area of the EZL.

As said previously, we improved earth/ground connections from battery neg to chassis and I was able to confirm much more solid continuity between battery neg and earth points around the EZL, including the common earth point on Pin 1 of the new EZL that now measures 0.09 ohms to battery neg.

Again, as said, these failures occurred after installation of new spark plugs and new NGK leads - no EZL failures in preceding 22 years! That was the only change aside from a cheap Chinese 12v USB charger but I cannot imagine how noise from that could destroy EZLs - maybe I'm wrong.

As always, thanks to all and KEEP THOSE IDEAS COMING!!!

R

 

[neilrr]

AFAIK # 95 32 is for a R129 300SL-24, the other 2 (20 & 21 32) are the later 'universal' 24v EZLs (one Bosch, one Siemens) which are interchangeable amongst the whole 24v range of cars.

Did you buy any of these new from MB? What do they say if you did?

 

[ivan1983]

If you are looking for spark leads arcing, I have spotted it in the dark when the engine bay is cold and has condensation on it, easily replicated by spraying a light mist of water over the engine bay. Although encouraging this behaviour might kill another EZL!

Also another one to check is that plug / leads impedance is the same as the old ones. I know at some point that they changed over from resistor in leads to plug to resistor in plug.

No resistance and you may have RF interference, too much and there might be an easier path for the spark to follow

 

[ivan1983]

Sorry just seen that you have checked this

 

[ray_hennig]

AFAIK # 95 32 is for a R129 300SL-24, the other 2 (20 & 21 32) are the later 'universal' 24v EZLs (one Bosch, one Siemens) which are interchangeable amongst the whole 24v range of cars.

Did you buy any of these new from MB? What do they say if you did?

The car originally had A0105459532 so was obviously new from MB. The two other spares (A0105459532 and A0125452132) were bought used.

The last, brand new A0125452032, now installed, was bought from MB in Bochum.

The EPC states A0105459532 (originally installed), replaced by A0125452032.

Both those are manufactured by Bosch.

A0125452132 is the Siemens-manufactured (not now available, apparently) version of A0125452032 - same spec.


R

 

[ray_hennig]

Update 19 June 2020

Continued to check electrical connections around battery. Noted the following:

The "front" controller - ABS I think - behind the battery was loose. Nuts that secure had not been tightened. Was this my fault? Possible. Would it cause any problems in earthing the unit? Is this a clue? I really don't think so but now we're in "desperation" territory so anything is considered.

The positive lead from the battery leads to a junction with numerous connection. They looked a bit corroded so were removed, Dremeled clean, copper greased and reinstalled.

Nothing else of an electrical nature looked suspicious so did general clean-up and reinstalled battery etc.

A new alternator and starter motor (both 30 years old) are on order and the local garage is on alert for installation when they arrive.

I'm trying to source a spare EZL of the following types:

A0125452032 (Bosch 0227400738

A0125452132 (Siemens EZ0051 5WK6 K30575HR1

A0105459532 (Bosch: 0027 400 736).

A0105459632 (Siemens: 5WK 301, I think)

PLEASE DOES ANYONE HAVE ONE OF THESE?

As always, thanks in advance for any comments, suggestions, EZLs!

Best to all.

RayH

 

[neilrr]

A couple of the first 2 EZLs are on Ebay UK.

 

[ray_hennig]

A couple of the first 2 EZLs are on Ebay UK.

Thanks for that and yes, I have seen those.

Frankly, their prices are still based on EZLs costing £2000+. They cost half that now.

There's one in France for 800€ and that's outrageous given the revised price. However, MB in France is still quoting 2300€.

Thanks again.

R

 

[neilrr]

What do you reckon is a fair price for 20 32 or 21 32?

 

[ray_hennig]

What do you reckon is a fair price for 20 32 or 21 32?

200 - 300 €?

R

 

[ray_hennig]

13 July 2020

Hello again All,

Well, I new, secondhand EZL has been installed. I am reluctant to install the "new" 1200 € one from MB until I am certain that the issues are solved. Time will tell.

Since the 3rd EZL failure, the following has been done.

1. New plugs, MB.

2. New leads, Beru.

3. New coil, MB.

4. Complete cleanup of all areas including distributor cap and rotor - only 9 months old.

5. Complete cleanup and reinstall of all earth straps, including the main engine strap underneath.

6. New (Bosch reconditioned) starter motor.

7. New (Bosch reconditioned) alternator.

Of course, I have no idea yet if all this has solved the problem. I shall not have confidence until a year (?) has passed. Even then 100% confidence is unlikely.

Just as before, the car now starts, drives and stops like a new car. Since its overhaul at PCS in 2017 it has never been better. Apart from this costly EZL issue.

Do I notice any differences after this latest set of "improvements"?

Yes, it now starts, even when hot, like a new car. Before, when hot, it would sometimes fire and then not keep running unless I kept the starter motor turning a little longer. That was hardly a problem as it was just a matter of remembering to hold the key in the start position for an extra half second.

However, it now seems to spring immediately into life and settle into an even idle under all circumstances. I shall be doing a more typical run today and shall be able to confirm this with greater confidence.

More as it happens.

And, as always, comments welcomed.

All the best.

RayH

 

[ray_hennig]

My last diagnosis will be measurements of the cable between the EZL and the coil. I've already verified this briefly but I'll do it now more aggressively by measuring the resistance whilst moving the cable to see if there's any intermittence.

And so it goes on.

R

 

[optimusprime]

Ray have you the old W124 work shop bible ? >>> Model 124 Maintenance Manual Index
'

 

[ray_hennig]

IS THIS A CLUE?

To recap; 3 EZLs blown in the past year despite almost new HT components, including coil.

I had the impression that death was at startup as I was vaguely conscious of a brief "fire" before death. We concluded that, possibly, some electrical surge was blowing these EZLs.

So, the latest measures included checking and cleaning all accessible earth/ground connections. And then a new (rebuilt by Bosch in Spain) starter motor and alternator have been installed.

Of course, I know not if I've solved it until the car does not fail to start for some time; a year, two years?

But, I have noticed one change.

Before, when closing the electric windows (front ones on a coupé - significant current), the revs would drop slightly and then recover.

After our measures and the new starter and alternator, when shutting the windows, absolute stability. No revs drop. Nothing.

I can't get too optimistic yet as the car was always performing like new - better by far than when I took delivery when it was 6 years old with 130k Kms (80k miles) on the clock.

What do we all think about that?

As always, best to all and keep those comments coming in.

RayH

 

[MercedesDriver]

Many years ago I had very similar problem with my BMW E21 and after I don’t know how much money spent with no result one of the “old” school technicians found out that the ignition barrel was faulty and the key was not fully returning to the position 2 after Start.

 

[ray_hennig]

Many years ago I had very similar problem with my BMW E21 and after I don’t know how much money spent with no result one of the “old” school technicians found out that the ignition barrel was faulty and the key was not fully returning to the position 2 after Start.

Thanks.

Yes, ignition switch considered and complete new switch/lock installed before EZL 3 bit the dust.

Barrel is only a few years old and feels like new.

R

 

[219]

Ray i think you know this,, but all original parts removed , must be replaced with the very same number ,and not just because it looks the same .Now another thing lots of these W124 had problems with the wire insulation cracking up and wires inside shorting in the loom .I would check the loom and cbles for bad wires . Ho and another thing,, as you have replaced the EZL did you replace the heat sink material [white type putty ] on the base before bolting it back on to the car body ?.

Hi - the biodegradable looms were not fitted to the 300-24 - only the 280 and 320 variants of the M104 , so that shouldn't be the issue here .

 

[219]

This is what we achieved today:

1. We identified that there was resistance of close to 1 ohm between battery negative and chassis - about 5 inches of earth cable. Deep clean, copper grease and now we have about 0.02 ohms. Continuity measurements between battery negative and earth points in the EZL area are now much easier to measure and much lower than previously.

2. We changed the spark plugs for genuine MB part: A0031596803.

3. Refitting the plug suppressors to the plugs was the same pain as I suffered with the NGK leads and the latest Beru leads. The quality of these latest (June 2019 and November 2019) NGK and Beru lead sets is not as good as the 2002 Beru lead set. I feel that the latest parts feel cheaper and they do not snap into place on the plugs so easily and, when installed, seem to pull off very easily.

4. We checked earthing of the coil - now close to 0.02 ohms from battery negative to coil body.

5. Coil primary resistance of new Beru coil measured (if I recall correctly) 0.15 ohms; whatever, it's same exactly as genuine MB item just received from Germany. So new Beru coil measuring exactly the same as unused MB coil. Important to note that this Beru coil was fitted after EZL failure number 2.

For today, that's it. Thinking and waiting for responses before next steps.

Thanks again and best to all.

RayH

Do you not still get Bosch leads for these cars ? Bosch was always my preference , just a personal thing . I know with the dizzy caps I haven't seen Bosch ones for years , and ended up using Beru in preference to Bremi ( which I tried once and had to replace in less than 10,000 miles .

 

[optimusprime]

Ray i have been checking up ,,and the EZL number 010 545 95 32 is specific for your model only and for no other model .. . So i hope this is the same as the one you fitted recently .

 

[ray_hennig]

Ray i have been checking up ,,and the EZL number 010 545 95 32 is specific for your model only and for no other model ..View attachment 99958 . So i hope this is the same as the one you fitted recently .

Thanks and noted. There's an update and the following are compatible:

Original: A0105459532 (Bosch 0027400736) or A0105459632 (Siemens: 5WK6 K30571HR1).

Updated: A0125452032 (Bosch 0227400738) or: A0125452132 (Siemens EZ0051 5WK6 K30575HR1).

My burnouts have involved 2 x A0105459532 (the original that came with the car and a 2nd hand buy) and 1 x A0125452132 (a 2nd hand buy).

Installed in the "perfect running" car is a second hand A0105459632.

In stock and tested is a brand new (well, built in 2003 and supplied to me by MB in Bochum earlier this year) A0125452032.

Thanks again.

R