I though of that, but it seems strange it would happen suddenly. It was running fine before the head gasket failed, it ran well for a whole day after the head gasket repair, then the next morning it just wouldn't fire up. That's what has me thinking electrical/timing.

I suppose I could disconnect the pipes to eliminate that possibility.

It did have what sounded like a backfire in the intake once or twice in this "trying to start" saga.