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ischmitz - If I understand your scope picture, if your ignition switch had been working correctly, there would be no voltage drop across it so the voltage at the hot side of the coil would not vary as the coil was charged and so would the scope show the ringing or just nothing? My guess is nothing, like the scope probe was connected to B+ and the battery would just sit at some constant voltage. Of course, during cranking, B+ probably varies quite a bit but with the engine running, it should be pretty smooth.
So I am guessing scott's engine will start right up and once it does, idling in the driveway, I'll have the A channel of the scope from coil hot to ground and the B channel from the low side of the coil to ground. The A channel should show around 14v pretty steady, the B channel should show pretty regular spikes and ringing, right?
If I do the same thing across the injectors, picking up the hot side of the injectors on one channel and the DME CPU side of the injectors on the other, again the hot side should be pretty steady and the CPU side should have the wave form that Rick referred to earlier.
If we get that far, we drive the car and watch the scope and see what changes when the engine turns off. We are going to look at injectors first and spark second.
Sound reasonable? I've yet to see the DME unit under the seat but I am assuming that I can get access to the necessary injector wiring somehow from there so that I don't have to try to run scope probes into the engine compartment.
Advice welcome.
Russ
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