Coils on those cars can cause considerable problems. I have had ones that would just make enough voltage to idle the car. I have had plenty that wouldn't do that. I have had at least one lead us astray by looking like it made usable spark. One needs to know that a 6-8000 volt spark won't get it, in the cylinder. I have a scope pattern of one of these at work. It took 10kv to idle once fixed. It was only getting 8kv cranking and the needs cranking were probably higher than idling.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician