1986 Mercedes Benz 560SECFACTORY OEM SERVICE PROCEDURE

Engine Running

  1. Run engine at idle (operating temperature). Check ignition timing (firing point). Nominal value should be 7-11°. If not okay, go to step 2). If okay, go to step 4).
  2. Pull plug from throttle valve switch connector. Test resistance of throttle valve switch on connector. Between terminals No. 1 and 2, idle speed position should be about zero ohms. Between terminals No. 2 and 3, full load position should be about zero ohms. Between terminals No. 1-2 and 2-3, partial load should be infinity ohms. If not okay, adjust or replace throttle valve switch. If okay, replace ignition control module.
  3. Run engine at 3200 RPM. Check ignition timing (vacuum line connected). Nominal value should about 40-44° ATDC at 3200 RPM. If not okay, go to step 4). If okay, go to step 6).
  4. Check vacuum line from intake manifold to ignition control module for leaks. If no leaks are present check resistance of reference resistor (EZL). Pull sensor signal input plug on ignition control module and check resistance with ohmmeter between connector terminal No. 3 and ground. Go to step 5).
  5. Nominal value should be about 750 ohms. If the nominal value is obtained, replace ignition control module. If the nominal value is not obtained, check wire for interruptions or replace plug that has a resistor. Go to step 6).
  6. Pull vacuum line from ignition control module and run engine at 3200 RPM. Check ignition timing. Nominal value should be about 27-31° at 3200 RPM. If okay, go to step 8). If not okay, go to step 7).
  7. Unplug coolant temperature sensor. Test resistance from sensor terminal to ground. See Figure (Coolant Temperature Sensor Resistance chart). Test resistance at 2 different temperatures. If these values are not okay, replace sensor. If values are okay, go to step 8).
  8. Run engine at 3200 RPM (vacuum line connected). Check dwell angle. Nominal value should be 24-53°. If not okay, replace ignition control module. If okay, test is complete.
Chapter Navigation
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.