I am testing the plug on the coil that the distributor cap plugs in to. This is a very early m104, with CIS-E like the M103. I'm not sure I follow where I would find three coils.

The car stalled a few times at red lights but would restart. Finally it stalled and hasn't restarted.

Recently we replaced the spark plugs and O2 sensor, but that doesn't seem relevant

We are not getting any power to the plug wires at all. This was tested by grounding a plug and by using a multimeter.

Today we replaced the distributor cap with no luck.