An eVCP camshaft phaser comprising a harmonic gear drive unit having a circular spline and a dynamic spline linked by a common flexspline, and a single wave generator disposed within the flexspline. The circular spline is connectable to either of a crankshaft-connectable sprocket or an engine camshaft, the dynamic spline being connectable to the other thereof. The wave generator is driven selectively by an eMotor to cause the dynamic spline to rotate past the circular spline, thereby changing the phase relationship between the crankshaft and the camshaft. A coaxial coil spring is connected to the sprocket and to the phaser hub and is positioned and tensioned to bias the phaser and camshaft to a stop position wherein the engine can run or be restarted after the eMotor is de-energized. Preferably, the spring comprises a spring cassette for easy assembly into the eVCP.