Originally Posted by Diesel911

I have no idea there.
The Element Plunger always has the same lenth of stroke on inline Fuel Injection Pumps.
It is how the Helix on the Plunger is Cut that determins what is called the "Effective Stroke" of the Plunger. Effective meaning the amount of the Stroke that is actually delivering Fuel.

As an example when the Element Plunger is rotated to the Shutoff Position the Plunger is still moving up and down as the Engine Rotates but the Plunger is rotated so the Helilx/Cut in the Plunger always exposes the Fuel Feed/Inlet Hole in the Barrel of the Element.
So in this case the Plungers effective stroke is zero and the Fuel that went into the the Element and is actually displace by the Plunger going up is expelled out of what I called the Fuel fill Hole (this violent expelling of Fuel is one of the reasons a Fuel Pressure Gauge Needle jumps).

The Time that the Helix covers the Fuel Feed Hole determins the length of Injection time (and amount of Fuel Injected) as does the rpm the Fuel Injection Pump is turning.

Simply put the amount of Injection Time is going to vary with the amount of Fuel Injected and the rpms of the Fuel Injection pump.
Someone who knows a lot about Physics and Math with the right measurements could calculate the speed of the Plunger moving up during Engine Rotation.

But, it is way easier to do the Measuremt as you are doing it now.