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Electronic ignition system with variable ignition characteristics and anti-knock control (EZL) - RA1500FLH0020X(15-0020)

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  1. Basic function diagram of electronic ignition system (EZL) 
    1. Engine 104 
      Fig 1: Basic Function Diagram Of Electronic Ignition System (EZL) (Engine 104)
      G04678816Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    2. Engine 119 
      Fig 2: Basic Function Diagram Of Electronic Ignition System (EZL) (Engine 119)
      G04678817Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Example, left bank of cylinders

    3. Engine 120 
      Fig 3: Basic Function Diagram Of Electronic Ignition System (EZL) (Engine 120)
      G04678818Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Example, left bank of cylinders

  2. Location of components 
    1. Engine 104 
      Fig 4: Identifying Electronic Ignition System (EZL) Components Location (Engine 104)
      G04678819Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Components in engine compartment

      Fig 5: Identifying Electronic Ignition System (EZL) Components Location (Components In Engine Compartment)
      G04678820Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Components on engine

    2. Engine 119 
      Fig 6: Identifying Electronic Ignition System (EZL) Components On Engine (Engine 119)
      G04678821Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Shown on model 140

      Components in engine compartment

      Fig 7: Identifying Electronic Ignition System (EZL) Components On Engine
      G04678822Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Components on engine

    3. Engine 120 
      Fig 8: Identifying Electronic Ignition System (EZL) Components - Components In Engine Compartment (Engine 120)
      G04678823Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Components in engine compartment

    Fig 9: Identifying Electronic Ignition System (EZL) Compartment On Engine Compartment
    G04678824Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Components on engine

  3. EZL block diagrams 
    1. Engine 104 
      Fig 10: EZL Block Diagrams (Engine 104)
      G04678825Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    2. Engine 119 
      Fig 11: EZL Block Diagrams (Engine 119)
      G04678826Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    3. Engine 120 

    Right bank of cylinders 

    Fig 12: EZL Block Diagrams - Right Bank Of Cylinders (Engine 120)
    G04678827Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Left bank of cylinders 

    Fig 13: EZL Block Diagrams - Left Bank Of Cylinders
    G04678828Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
  4. Ignition coil 

    In engine 104 one, in engines 119 and 120 one ignition coil for each of the two banks of cylinders, is used, with a separate ignition system being used in engine 120 for each bank of cylinders.

    Location, see "B".

  5. Firing order 
    Fig 14: Identifying Firing Order (Engine 104)
    G04678829Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    Fig 15: Identifying Firing Order (Engine 119)
    G04678830Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    Fig 16: Identifying Firing Order (Engine 120)
    G04678831Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
  6. EZL ignition control unit 
    1. General 

      An ignition map for vehicles with catalytic converter and an ignition map for vehicles without catalytic converter is stored in the EZL ignition control unit (N1/3, engine 120 N1/4 and N1/5).

      Faults which occur when the engine is running are counted by a fault counter.

      Only if a fault occurs during more than 8 successive trips it is entered into the fault memory after the engine is switched off and can be read with the pulse counter.

      If the fault then no longer occurs, it is erased again after a certain number of starts.

      Only faults which prevent the engine from starting or severely affect engine running are stored immediately. The fault memory is not

      Fig 17: Identifying EZL Ignition Control Unit
      G04678832Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      erased when the battery is disconnected. The stored faults can be read with the pulse counter at the test coupling for diagnosis (X11/4) (see Diagnosis Manual Engine Volume 2).

      IMPORTANT

      The fault memory should be read when the engine is not running and the ignition is switched on.

      The idle speed and full load signals are passed by the actuator at the throttle valve via the electronic accelerator pedal control unit (N4/1) or idle speed control/Tempomat control unit (N4/3), depending on the equipment, to the EZL ignition control unit.

    2. Assignment of ignition control units (engine 120) 

      The assignment (coding) of the two ignition control units to the corresponding bank of cylinders is performed via coupling "A" contact "6".

      If contact "6" is not assigned, this ignition control unit is assigned to the right bank of cylinders (cylinders 1-6), viewed in direction of travel. If ground exists at contact "6", this ignition control unit is assigned to the left bank of cylinders (cylinders 7-12).

      Fig 18: Identifying Ignition Control Units (Engine 120)
      G04678833Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    3. Assignment of couplings 
      ASSIGNMENT OF COUPLINGS

        Engine 104 Engine 119 Engine 120
      1 3-pin coupling knock sensors:
      1. Common ground
      2. Knock sensor 1
      3. Knock sensor 2
      		 3-pin coupling knock sensors:
      1. Common ground
      2. Knock sensor 1 (left side of engine)
      3. Knock sensor 2 (right side of engine)
      		 3-pin coupling knock sensors:
      1. Common ground
      2. Knock sensor 1 (left side of engine)
      3. Knock sensor 2 (right side of engine)
      2 Coaxial connector for control cable from crankshaft position sensor Coaxial connector for control cable from crankshaft position sensor Coaxial connector for control cable from crankshaft position sensor
      3 EZL resistance trimming coupling (R16/2) EZL resistance trimming coupling (R16/2) Left EZL resistance trimming coupling (R16/3)
      Right EZL resistance trimming coupling (R16/4)
      4 Vacuum connection Vacuum connection Vacuum connection
      A 8-pin coupling:
      1. Ignition coil (T1) terminal 1
      2. Ground terminal 31
      3. Terminal 15
      4. TN signal
      5. Negative, position sensor/ cylinder recognition
      6. Vacant
      7. Pulse output
      8. Camshaft position sensor (L5/1) signal output
      		 8-pin coupling:
      1. Ignition coil (T1/2) terminal 1
      2. Ground terminal 31
      3. Terminal 15
      4. TN signal
      5. Negative, position sensor/ cylinder recognition
      6. Ignition coil (T1/1) terminal 1
      7. Pulse output
      8. Camshaft position sensor (L5/1) signal output
      		 8-pin coupling:
      1. Ignition coil (T1/1, T1/2) terminal 1
      2. Ground terminal 31
      3. Terminal 15
      4. TN signal
      5. Negative, TN signal/ cylinder recognition/ diagnostic output
      6. 6 left: ground (coding for left bank of cylinders, cylinders 7-12), right: vacant
      7. Pulse output and serial diagnosis interface
      8. Camshaft position sensors (L5/2, L5/3) signal output
      B 8-pin coupling:
      1. Camshaft position sensor (L5/1) signal input
      2. Transmission overload protection
      3. Data line
      4. Data line
      5. Ground, camshaft position sensor
      6. Ground, data line
      7. Vacant
      8. Terminal 30
      		 8-pin coupling:
      1. Camshaft position sensor (L5/1) signal input
      2. Transmission overload protection
      3. Data line
      4. Data line
      5. Ground, camshaft position sensor
      6. Ground, data line
      7. Vacant
      8. Terminal 30
      		 8-pin coupling:
      1. Camshaft position sensors (L5/2, L5/3) signal input
      2. Transmission overload protection
      3. Data line
      4. Data line
      5. Ground, camshaft position sensor
      6. Ground, data line
      7. Vacant
      8. Terminal 30

      Engine 104 

      The EZL ignition control unit features a power output stage which actuates an 11 A ignition coil (T1).

      Fig 19: Identifying EZL Ignition Control Unit (Engine 104)
      G04678834Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      The high voltage is distributed through the high voltage distributor (S5/3) in the firing order 1-5-3-6-2-4.

      The moving carbon in the distributor has been replaced by a fixed central electrode.

      Fig 20: Identifying High Voltage Distributor In Firing Order
      G04678835Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
      Fig 21: Identifying Distributor Components
      G04678836Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Engine 119 

      The EZL ignition control unit features two separate power output stages each of which actuates an 11 A ignition coil (T1/1, T1/2).

      Fig 22: Identifying EZL Ignition Control Unit (Engine 119)
      G04678837Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      The high voltage is likewise distributed through two separate high voltage distributors (S5/5, S5/6).

      The high voltage distributor (S5/6) distributes the high voltage to cylinders 1, 4, 6 and 7, the high voltage distributor (S5/5) to cylinders 5, 8, 3 and 2.

      The moving carbon in the high voltage distributor has been replaced by a fixed central electrode.

      Fig 23: Identifying High Voltage Distributor Distributes High Voltage To Cylinders
      G04678838Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
      Fig 24: Identifying Distributor Components
      G04678839Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Engine 120 

      The EZL ignition control units each feature a power output stage which actuate an 11 A ignition coil (T1/1, T1/2).

      Fig 25: Identifying Ignition Coil 1 (Right Bank Of Cylinders)
      G04678840Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
      Fig 26: Identifying Ignition Coil 2 (Right Bank Of Cylinders)
      G04678841Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      The high voltage is distributed through two separate high voltage distributors (S5/5, S5/6). The high voltage distributor (S5/5) distributes the high voltage to the left bank of cylinders (cylinders 7-12) in the firing order 12-8-10-7-11-9, the high voltage distributor (S5/6) to the right bank of cylinders (cylinders 1-6) in the firing order 1-5-3-6-2-4.

      The moving carbon in the high voltage distributor has been replaced by a fixed central electrode.

      Fig 27: Identifying High Voltage Distributors
      G04678842Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
      Fig 28: Identifying Distributor Components
      G04678843Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    4. EZL resistance trimming coupling 

      The ignition map for KAT or without KAT is activated via the resistance trimming coupling (R16/2, engine 120 R16/3 and R16/4).

      The ignition is set for unleaded premium grade fuel with an octane rating of RON 95.

      If regular grade fuel with e. g. an octane rating of RON 91 is used, a suitable resistance trimming coupling (R16/2, engine 120 R16/3 and R16/4) must be installed (see Diagnosis Manual Engine, Volume 1).

      Fig 29: Identifying Resistance Trimming Coupling
      G04678844Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
      NOTE: If regular grade fuel is used, the ignition timing is retarded by the anti-knock control which increases the overall temperature level of the engine. For this reason, regular grade fuel should only be used if, in exceptional cases, no premium unleaded or premium plus is available (see also Owner's Manual).
    5. TN signal 

      The EZL ignition control unit converts the sinusoidal signal of the crankshaft position sensor into a square wave signal - TN signal.

      The conversion to the TN signal has become necessary as the ignition timing for each cylinder in the knock control range may differ. The TN signal can be measured in exactly the same way as the TD signal.

      The signal is passed by the EZL ignition control units to the respective LH control unit and from there to the base module.

    6. Synchronization signal for fuel injection system 

      The injection sequence must be synchronized to ensure that the moment of injection is correctly matched to the respective cylinder. The signal of the camshaft position sensor (L5/1, engine 120 L5/2 and L5/3) is required for this purpose.

      The camshaft position sensor generates two alternating voltage signals during each rotation of the camshaft. These are processed to square wave signals in the EZL ignition control unit and passed to the LH control unit.

      Fig 30: Identifying Camshaft Position Sensor
      G04678845Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    7. Coolant temperature signal 

      This signal is passed by the coolant temperature sensors (B11/2, engine 120 B11/9 and B11/10) to the respective LH control unit and from there via the CAN databus to the respective EZL ignition control unit.

      Fig 31: Identifying Coolant Temperature Sensors (Engine 104)
      G04678846Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
      Fig 32: Identifying Coolant Temperature Sensors (Engine 119)
      G04678847Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
      Fig 33: Identifying Coolant Temperature Sensors (Engine 120)
      G04678848Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    8. Safety measures 

    Should one of the coolant temperature sensors fail, a substitute temperature of 120 °C is selected. As this temperature is within the boiling protection range, the ignition timing advance is retarded by 3.5° CA.

  1. G. Anti-knock control (AKR) 

    Should the load sensor in the EZL ignition control unit fail, full load is assumed to thus activate the anti-knock control. Should the knock sensors, the analysis circuit in the EZL ignition control unit and/or the camshaft sensor fail, ignition timing is retarded 10° CA as a safety measure.

    1. Block diagram 
      Fig 34: Anti-Knock Control (AKR) - Block Diagram
      G04678849Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    2. Function 

      The ignition maps of the ignition system (EZL) are designed for optimal engine output. Should knocking combustion occur under certain operating conditions, the knocking cylinder is detected in the respective EZL ignition control unit by the integrated anti-knock control and ignition timing is retarded accordingly.

      Knocking combustion may occur, for example, as a result of poor fuel quality and deposits in the combustion chambers.

      The anti-knock control has been developed to avoid damage as a result of knocking combustion. The anti-knock control is integrated in the EZL ignition control unit.

      Fig 35: Fuel Quality Graph
      G04678850Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Pressure curve in combustion chamber during normal combustion

      Fig 36: Combustion Chamber Pressure Graph
      G04678851Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Pressure curve in combustion chamber during knocking combustion

      Fig 37: Combustion Chamber Pressure Graph
      G04678852Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      The "KAT" or "without KAT" ignition map in the EZL ignition control unit is activated by fitting on an appropriate resistance trimming coupling (R16/2, engine 120 R16/3 and R16/4).

      Should knocking combustion occur as a result, e. g. of fuel with a low octane number, the mechanical vibrations produced are converted in the knock sensors into electrical signals and passed to the respective EZL ignition control unit.

      The EZL ignition control unit compares these incoming signals with the specifications stored in the integrated microcomputer.

      If deviations exist, the ignition timing for the cylinder in which knocking combustion has taken place is retarded by 3° CA as early as the next ignition.

      Should the cylinder continue to knock, ignition timing is retarded by a further 3° CA.

      This retardation of ignition timing may be repeated if knocking combustion continues to exist until a maximum retardation is reached, this being dependent on coolant temperature (e. g. 12 ° CA at 80-90 °C coolant temperature).

      Fig 38: Identifying Resistance Trimming Coupling
      G04678853Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Several knocking combustions in a cylinder

      Fig 39: Cylinder Knocking Combustions Chart
      G04678854Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

      Should no further knocking combustion occur, the ignition timing of the cylinder in question is restored to the map value by being advanced 0.35° CA per ignition.

      An additional signal is required for detecting the cylinders for the anti-knock control. This alternating voltage signal comes from the camshaft position sensor (L5/1, engine 120 L5/2 and L5/3).

      Engines 104 and 119 each have a camshaft position sensor (L5/1) which detects cylinder 1. Engine 120 has two camshaft position sensors (L5/2 and L5/3) which detect cylinders 1 and 7.

      Should one of the following components fail, an ignition timing retardation dependent on coolant temperature is activated for all cylinders for safety reasons:

      • Knock sensors,
      • knock sensor analysis circuit of anti-knock control in EZL ignition control unit,
      • camshaft position sensor (L5/1, engine 120 L5/2 and L5/3).

      Examples for retardation of ignition timing dependent on coolant temperature:

      10° CA at 100 °C coolant temperature

      7° CA at 80 °C coolant temperature

      To facilitate fault finding, faults at certain components can be interrogated by means of a pulse readout (flash code).

    3. Knock sensor units 

    Piezo electric structure-borne sound sensors are used as knock sensors (A16, engine 120 A 29 and A30).

    The vibrations of the engine block are transmitted to the piezo ceramic and passed in the form of an alternating voltage signal along a screened wire to the EZL ignition control unit.

    A knock sensor unit consists of two knock sensors which are combined in a cable and can thus only be replaced as a unit.

    Fig 40: Identifying Knock Sensor Cable
    G04678855Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Engine 104, 119

    NOTE: Piezo effect=generation of voltage as a result of pressure acting on a certain ceramic.
    Fig 41: Identifying Knock Sensor Cable - Right And Left
    G04678856Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Engine 120

    Engine 104 

    The knock sensors (arrows) are attached to the engine block below the intake manifold. This location point has been selected as it is the best location to detect knocking combustion at all cylinders.

    Fig 42: Locating Knock Sensor (Engine 104)
    G04678857Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Engine 119 

    The knock sensors are attached to the engine block in each case below an engine carrier. This installation point has been selected as it is the best point to detect knocking combustion at all cylinders.

    Fig 43: Locating Knock Sensor (Engine 119)
    G04678858Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
    Fig 44: Locating Knock Sensor (Left Side Of Engine)
    G04678859Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Engine 120 

    The knock sensors (A29) and (A30) are attached to the insides of the engine block between the banks of cylinders. This installation point has been selected as it is the best point to detect knocking combustion at all cylinders. The cables of the two knock sensors for each side of the engine are combined in a protective sheath (flexible sheath).

    Fig 45: Locating Knock Sensor (Engine 120)
    G04678860Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
  2. H. Camshaft position sensors 

    Two position pointers are arranged at the camshaft sprocket, offset relative to each other. This enables the cylinders to be detected during each revolution of the crankshaft for synchronization of injection sequence as well as for the anti-knock control.

    The injection sequence for the cylinders is synchronized during the starting operation. In order to obtain a strong signal already at starting speed, the air gap between position sensor and position pointer must only be 0.4-0.6 mm. When performing repairs, the air gap must be checked and set, if necessary, with spacers (see repair instructions).

  3. I. Catalytic converter heating up 

    The exhaust temperature is increased in order to heat up the catalytic converter more rapidly to its operating temperature.

    For this purpose, the ignition timing, at idling speed and with selector lever in P or N, is continuously retarded at a coolant temperature between approx. +15 °C and +40 °C after each start for about 30 seconds depending on temperature, and idling speed is increased by the idle speed control to 1100-1200/min. The idle speed increase is deactivated once a Drive mode has been engaged.

  4. J. Transmission overload protection 

    General 

    In order to protect the shift elements or the automatic transmission from excessive thermal stresses during power shifts in the top engine speed range, a transmission overload protection is integrated in the EZL ignition control units.

    As a result of the transmission overload protection, ignition timing is retarded to 5° CA before TDC for about 400 ms (reduced engine torque) during 1 → 2 and 2 → 3 upshifts (engine 120: 1 → 2, 2 → 3, 3 → 4).

    As this retardation of ignition timing during the shifting phase also provides a smoother gearshift, this measure is also used during 3 → 2 full load downshifts (engine 120: 4 → 3 and 3 → 2). Ignition timing is retarded provided the following conditions are met simultaneously:

    • Engine speed >4000/min (reference value)
    • Vacuum in intake manifold <300 mbar (reference value)
    • Shift signal from transmission overload protection switch, brake band B1 (S65) (engine 120: brake band B1 (S65) or B2 (S65/1)).

    The transmission overload protection switch, brake band B1 (S65) (engine 120: brake band B1 (S65) and B2 (S65/1)) is designed as a hydraulic switch and linked to the operating pressure circuit of brake band "B1" and "B2", respectively, of the automatic transmission.

    The opening and closing of the transmission overload protection switch, brake band B1 (S65) (engine 120: brake band B1 (S65) and B2 (S65/1)) is detected as a shift signal by the appropriate EZL ignition control unit. The shift function of the transmission overload protection switch, brake band B1 (S65) is dependent on the working pressure which exists at "B1".

    Working pressure <1.8 bar: S65 opened.

    Working pressure >1.8 bar: S65 closed.

    Fig 46: Identifying Brake Band
    G04678861Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Engine 120 

    The shift function of the transmission overload protection switch, brake band B2 (S65/1) is dependent on the working pressure which exists at "B2".

    Working pressure <1.8 bar: S65/1 opened.

    Working pressure >1.8 bar: S65/2 closed.

    The opening and closing of the transmission overload protection switch, brake band B1 (S65) and B2 (S65/1) is detected as a shift signal by the appropriate EZL ignition control unit.

    Fig 47: Identifying Brake Band (Engine 120)
    G04678862Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

    Emergency running mode transmission overload protection 

    If the EZL ignition control unit does not receive a shift signal from the automatic transmission when driving, whether as a result of a fault at the transmission overload protection switch, brake band B1 (S65) or brake band B2 (S65/1) or at the wiring, the appropriate EZL ignition control unit switches to emergency running mode. The transmission overload protection is active only to a restricted extent in the emergency running mode.

    If no shift signal is received from the automatic transmission, the EZL ignition control unit recognizes the start of a gearshift as a result of a change in engine speed of a defined magnitude. If the transmission overload protection is operating in the emergency running mode, this may make itself noticeable as a result of a brief retardation of ignition timing at high speed. In the event of the complaint "misfiring at high speed" the transmission overload protection switch, brake band B1 (S65) and brake band B2 (S65/1) as well as the appropriate wiring should be checked.

  5. K. Engine torque reduction in ASR control mode 

    General 

    Ignition timing is briefly retarded if the vehicle speed is >20 km/h during the initial ASR control cycle in order to achieve an immediate reduction in engine torque when the wheels begin spinning until the throttle valve control is activated.

    The signal which is required to activate the EZL ignition control unit in this case is supplied by the electronic accelerator pedal control unit.

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