testing optispark
05-11-2014, 08:54 PM
#2
Race Director
If your car wont start...watch the tach needle while cranking.
If it doesnt jiggle while cranking, the ecm isnt getting a signal from it. The ecm gets the rpm from the optispark.
All that said, that is not the end all test. You could be getting a signal for the tach and ecm, but could be getting shorts on the high voltage side. in those cases, the car usually runs, but misses/stumbles, especially when warmed up and under a load
If it doesnt jiggle while cranking, the ecm isnt getting a signal from it. The ecm gets the rpm from the optispark.
All that said, that is not the end all test. You could be getting a signal for the tach and ecm, but could be getting shorts on the high voltage side. in those cases, the car usually runs, but misses/stumbles, especially when warmed up and under a load
05-11-2014, 10:41 PM
#3
05-12-2014, 06:02 PM
#4
Instructor
Thread Starter
opti spark
thanks all great info. Tach is not responding. The car will run for 10 minutes and then stall. Will rollover but not start for a few hours after sitting. Replace opti spark 2 years ago (within 2k miles) ecm also rebuilt 2 years ago.