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Thread: Video & photos of failed EZL internals

  1. #1
    .036 Hoonigan™
    E500E Boffin
    gsxr's Avatar
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    Dec 2008
    Boise, ID, USA

    Video & photos of failed EZL internals

    Couple of interesting videos from a fellow in Australia. Source is this thread on Ben's Whirled, post #42-43. I think this is a late M117 EZL, not M119, but the principles should be similar and both drive distributor ignition systems. From the description for the video below:

    "It is of my unprofessional opinion that the coil switching transistor [EZL] failure is a symptom of the failure and not the root cause.

    The affected vehicle had a poorly maintained ignition system. It is of my opinion the damage to this custom silicon in the EZL was caused by excessive inductive spiking from the ignition coil as a result of the poor condition secondary (HV) components. With this dead short the coil switching transistor is held ON permanently and as such its fly lead to ground simply vaporised under the current available from the car battery. This die only runs on extremely low current 5VDC and the damage can be explained no other way."

    This BW thread had some interesting photos inside an M117 EZL.

    And, this thread has photos inside an M119 / 500E EZL.

    What really happens to an EZL with a poorly maintained ignition system?

    Dave M.
    1997 E420 (Bugeyes)
    1994 E420 (Blondie)
    1994 E500 (Q-ship)
    1992 500E (Mach 5)
    1987 300D (Sportline Stage 2)
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  2. The Following 6 Users Say Thank You to gsxr For This Useful Post:

    500AMM (01-12-2018), JC220 (01-12-2018), nocfn (01-12-2018), S70/2 (01-12-2018), sheward (01-12-2018), TerryA (01-12-2018)

  3. #2
    Site Honcho
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    gerryvz's Avatar
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    Nov 2008
    Annapolis, MD

    Re: Video & photos of failed EZL internals

    For US-spec cars, the aluminum-block M117 EZL units as found in the 5.6-liter engines are outwardly similar looking, but of a very different functional design than the LH-based (119.97X) EZLs. For 1991 126 models optionally specified with ASR I, late M117s had AKR (anti-knock) and the design is more (but not exactly) similar to that of the 119.97X.

    Interestingly, non-AKR M117 EZL units (aka US 5.6L) are not particularly known to fail, though as with anything, it does happen. I've seen units that have seemingly gone through nuclear blasts, and work fine. My SEC is still on its original EZL, at nearly 250K miles, and no issue. If there ever is, I have 4-5 spares waiting in the wings.

    M119 EZL units seem to be much more susceptible to ignition (coil/cap/rotor/wires) issues. Knowledgeable sources have told me in the past, that Bosch units are also less reliable overall than Siemens units.

    The biggest issue, IMHO, with EZL unit failures is "cooking" of the units because they get overheated due to heat transfer paste failure.

    I did a HOW-TO on paste replacement last year, and it is a preventative maintenance item that EVERYONE should do. My Bosch EZL failed on my E500 back in early 2009, just after I moved to Texas. One complete bank of the engine was lost. New Siemens 036-specific EZL, which I'd literally just purchased weeks before for $800, made the car like new again.

    Paste replacement HOW-TO is here.


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  5. #3
    Site Honcho
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    gerryvz's Avatar
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    Nov 2008
    Annapolis, MD

    Re: Video & photos of failed EZL internals

    - Banzworld .... check
    - 126 sub-forum .... check
    - mcClare bragging posting about circuit repair prowess .... check

    Yep. Great thread !!

    At least the photos are good though

  6. The Following 2 Users Say Thank You to gerryvz For This Useful Post:

    gsxr (01-12-2018), TerryA (01-12-2018)

  7. #4
    E500E Guru JC220's Avatar
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    Feb 2016

    Re: Video & photos of failed EZL internals

    Wow I have a whole new appreciation for what’s inside EZL’s now!
    1987 w124 200 - 3.6 AMG build | 1990 w124 300E-24 | 1992 w124 500E

    1994 320CE Sportline | 1997 w140 S280 | 2007 w211 E220CDI | 1994 220CE

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