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Home >> Mercedes Benz >> 1991 >> 560SEC >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> EZL Ignition System >> Engine Running
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Engine Running

  1. Run engine at idle, at operating temperature. Check ignition timing to be 7-11 degrees. If timing is not 7-11 degrees, go to next step. If timing is 7-11 degrees, go to step 4).
  2. Unplug throttle valve switch connector. Test resistance of throttle valve switch at connector terminals. Resistance reading between terminals No. 1 and 2 in the idle speed position should be about zero ohms; reading between terminals No. 2 and 3 in wide open throttle position (full load position) should be about zero ohms; reading between terminals No. 1 and 2 and terminals No. 2 and 3 in middle position of lever travel (partial load) should be infinity.
  3. If readings are not as specified, adjust or replace throttle valve switch. If reading are as specified, replace ignition control module (EZL).
  4. Run engine at 3200 RPM. Check ignition timing (with vacuum line connected on models so equipped) to be 40-44 degrees ATDC at 3200 RPM. If timing is not as specified, go to next step. If timing is okay, go to step 6).
  5. Check vacuum line from intake manifold to ignition control module for leaks. If no leaks are present, check resistance of reference resistor for EZL. Pull sensor signal input plug on ignition control module (Brown/Yellow Green/ Black wire). Using ohmmeter, check resistance between harness connector terminal No. 3 and ground.
  6. Resistance should be 750 ohms. If resistance is as specified, replace ignition control module. If resistance is not as specified, check wire for open or replace connector. Go to next step.
  7. Pull vacuum line from ignition control module and run engine at 3200 RPM. Check ignition timing to be 27-31 degrees at 3200 RPM. If timing is correct, go to step 9). If timing is incorrect, go to next step.
  8. Unplug coolant temperature sensor. Test resistance across sensor terminals and refer to chart for specification. See Figure and Figure. Test resistance at 2 different coolant temperatures. If resistance is not within specifications, replace coolant temperature sensor. If resistance values are okay, go to next step.
  9. Run engine at 3200 RPM (vacuum line connected). Check dwell angle to be 24-53 degrees. If dwell angle is not correct, replace ignition control module. If dwell angle is okay, test is complete.
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