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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3567
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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560SL: 1988 560am. Quit @ 55mph. Has fuel, no spark. Bad c

Customer Question

1988 560am. Quit @ 55mph. Has fuel, no spark. Bad coil?
Submitted: 2 years ago.
Category: Mercedes
Expert:  Marty replied 2 years ago.
Hi, if you have no spark from the coil the possibilities are a bad coil, bad ignition module or a bad crankshaft sensor. You need to see if you are getting a pulse to the negative terminal on the coil when cranking the motor. Connect a test light to ground and turn the key on. Probe the negative side of the coil for voltage. You should have 12 volts with the key on. Next crank the motor and see if the test light flashes or pulses. If it does I would try a new coil. If you get no pulse you either have a bad crank sensor or a bad ignition control module.