Interesting... You can also use an electret mic and audio amp to trigger a standard inductive pickup timing light. I drew a drawing for this quite a while back. Here is the drawing, I am not sure if the parts are still available from Radio Shack though as this was discussed quite a long while back:)
Using this device, the live running timing with the spill timing set correctly on mine was around 1 degree or less before TDC if I recall correctly.
When you did your spill timing, did you unscrew the top fitting off of the injector pump and remove the little check valve core and spring? It is under the fitting that the lower end of the injector hardline connects to, and easilly missed. IF you don't remove that check valve core, fuel cannot flow freely thru the pump when the pump piston is low enough to expose/open the port. The spill timing point is the point that the IP fuel inlet port just closes(start of the pump stroke where fuel pressure just starts to build). So fuel should flow freely before the spill point and stop right at the spill timing point. You have to be carefull because if you continue to turn the wheel the pump piston will give the impression that fuel is still flowing. One way I do it is to start with the wheel between the spill point and TDC. this is where i remove the pump top fitting and check valve. I reverse the wheel ahead of the spill point untill fuel just starts to flow out the top, then I move the wheel a little in it's normal direction of rotation and stop. Then I watch to see if the fuel stops. If not, move a bit more and stop then look at the flow, repeate untill the fuel has stopped. Onother way I have done it is to set that little check valve core rod into it's hole. It will set there and keep fuel from flowing when the port is open by it's weight alone. Once the port closes, the piston will push fuel upward and that little valve core will lift up. the point where the core first starts to move should be the spill point.
Your method has potential for error, as does my audio pickup/inductive trigger. At what point exactly are you and your ear calling the injector fired? At what point exactly is my amp triggering the timing light? I did some experiments with my setup using the triggered strobe to look at the injector spraying fuel outside the engine. The spray cloud starts, builds in size then dissipates. The timing light fired just after the start of the spray, but is this considered the "firing point"? I have no idea... We also do not know exactly where the running timing is supposed to be anyway. The only timing spec for these engines IS the spill timing point...
As always my .02